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Timeline/Chronology of Astronomy and Space Technology

ca. 10000000000 BCE __ Our Galaxy, the Milky Way, is probably formed around this time.    Our Sun and our Solar System are formed.    The hydrogen and helium atoms in the young universe begin to form into areas of greater and lesser density. The dense patches form into clusters of galaxies under the force of gravity. The universe emerges from a state of extremely high temperature and density in an event known as the Big Bang.

2700 BCE A lunar calendar is developed in Mesopotamia in which new months begin at each new Moon. A year is 354 days long and the calendar is used primarily for administrative purposes.
2296 BCE _ The Chinese record the earliest sighting of a comet.
2100 BCE _ An intercalated month is added to the Sumerian calendar to bring the lunar calendar in line with the solar year.
1361 BCE _ Chinese astronomers make the first recording of an eclipse of the Moon.
1300 BCE The Egyptians have identified 43 constellations and are familiar with those planets visible to the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn.    The Shang dynasty in China establishes the solar year at 365 1/4 days. The calendar consists of 12 months of 30 days each, with intercalary months added to adjust the lunar year to the solar.
1217 BCE _ Chinese astronomers make the first recording of an eclipse of the Sun.
763 BCE _ 15 JUNE: Assyrian archivists record an eclipse of the Sun. The same event is recorded in the Bible (Amos 8:9).
648 BCE _ 6 APRIL: Greek poet Archilochus records a total eclipse of the Sun.
585 BCE _ 28 MAY: The Greek philosopher Thales of Miletus, pioneer of Greek rational thinking, correctly predicts the eclipse of the Sun.
432 BCE _ Athenian astronomer Meton accurately calculates the 19-year cycle when lunar phases recur on the same days of the solar year -- the Metonic cycle.
366 BCE _ Greek mathematician and astronomer Eudoxus of Cnidus builds an observatory and constructs a model of 27 nested spheres to give the first systematic explanation of the motion of the Sun, Moon, and planets around the Earth.
352 BCE _ Chinese astronomers make the earliest known record of a supernova.
350 BCE _ Greek astronomer Heracleides is the first to suggest that the Earth rotates and that the motion of Mercury and Venus is influenced by their revolution around the Sun.
300 BCE _ Babylonian astronomer Berosus invents the hemispherical sundial. It consists of a block of stone or wood with a hemispherical opening with arcs inscribed on the inner surface. Time is reckoned by the position of the shadow of a pointer, which is attached to the outer part of the hemisphere, as it crosses the arcs.
280 BCE _ Greek astronomer Aristarchus of Samos writes On the Size and Distances of the Sun and the Moon. He is the first to maintain that the Earth rotates and revolves around the Sun.
240 BCE _ Chinese astronomers make the first recorded sighting of Halley's Comet.
200 BCE _ Chinese scholars recognize a relationship between tides and the phases of the Moon. The Greeks invent the astrolabe—the first scientific instrument. It is used for observing the positions and altitudes of stars.
165 BCE _ Chinese astronomers first observe and record sunspots. Continuous records of sunspots are kept by Imperial astronomers from 28 BCE to 1638 CE.
150 BCE _ Greek scientist Hipparchus of Bithynia builds an observatory on the island of Rhodes, containing instruments to measure accurately the positions of celestial bodies.
129 BCE _ Greek scientist Hipparchus of Bithynia creates the first known star cata log. It gives the latitude and longitude and brightness of nearly 850 stars and is later used by Ptolemy.
127 BCE Greek scientist Hipparchus of Bithynia discovers the precession of the equinoxes and calculates the year to within 6.5 minutes. He also makes an early formulation of trigonometry.
80 BCE The Greek philosopher Poseidonius estimates the circumference of the Earth by measuring the distance from Rhodes to Alexandria, and by using the difference in the height of the star Canopius above the horizon at each location to estimate the angle of arc. His estimate is 11% too large.
128 _ The Greek mathematician and astronomer Theon of Smyrna observes a transit of Venus across the face of the Sun. Since this is incompatible with the earth-centered model of the universe, he suggests Venus and Mercury orbit the Sun.
139 _ The Egyptian astronomer Claudius Ptolemy is making observations in Alexandria, formulating his geocentric (earth-centered) model of the universe.
140 _ Egyptian astronomers at Alexandria devise an armillary sphere with nine circles as a complete representation of the universe and a calculating aid for astronomy.
150 _ The Greek astronomer Claudius Ptolemy publishes the work known as the Almagest, a highly influential astronomical textbook that outlines a theory of a geocentric (Earth-centerd) universe based on years of observations.
346 _ 6 JUNE: During a total eclipse of the Sun, astronomers record that the stars become visible in daylight—the first time they have recorded this phenomenon.
400 _ Egyptian astronomer and mathematician Hypatia distinguishes herself as one of the first women scientists, becoming head of the Neo-Platonist school at Alexandria, and a widely consulted authority on matters of physics and mathematics.
516 _ The Indian astronomer and mathematician Aryabhata I produces his Aryabhatiya, a treatise on quadratic equations, the value of p, and other scientific problems, in which he adds tilted epicycles to the orbits of the planets to explain their movement.
657 _ Pacal, the new Lord of Pallenque, a Mayan religious center in southern Mexico, founds an observatory and builds astronomical monuments, including his own tomb, aligned to the winter solstice.
725 _ The Chinese astronomer and monk I Hsing, using instruments made by engineer Liang Ling-Tsan, measures the deviation of star coordinates from their expected values, taking precession from the Earth's orbit into account. In this way, he discovers the 'proper motion' of the stars.
772 _ Muslim astronomer Al-Fazari translates the Indian astronomical compendium Mahasiddhanta/Treatise on Astronomy, and begins the establishment of a uniquely Arabic astronomy.
800 _ The Peruvian city of Machu Picchu, built at this time, contains an astronomical altar, 'the hitching post of the Sun', which can be used to measure solar and lunar movements with great accuracy.
815 The Muslim scholar Masha'allah writes on astrology, the astrolabe, and meteorology. As court astrologer, he was responsible for choosing a propitious date for the founding of the new capital at Baghdad.
827 Muslim scholar Al-Hajjaj translates the 2nd-century Egyptian astronomer Ptolemy's Great Mathematical Compilation into Arabic, as al-Majisti. It is later known as simply the Almagest.
850 _ Persian mathematician and astronomer Al-Khwarizmi dies, having written The Calculation of Integration and Equation—Image of the World, with a map of the world and heavens, and his zij, a collection of influential astronomical tables.
877 _ Arab astronomer Al-Battani begins his observations at al-Raqqah observatory in Syria. He refines the calendar and demonstrates the possibility of annular eclipses, in which the Moon obscures most of the Sun, but leave s a bright ring around the edge.
886 _ Islamic astronomer Abu Ma'shar writes a treatise on tides, among various attempts to synthesize Greek, Persian, and Indian astronomy. Other Arab scholars attack him for his belief in astrology, however.
900 _ Al-Battani writes his Zij, a collection of astronomical tables for calculation of celestial motions. He is one of the first astronomers to recognize the need for observation to confirm calculation.
970 _ The Muslim astronomer Abu al-Wafa' invents the wall quadrant for the accurate measurement of the declination of stars in the sky. He also discovers, and plots tables for, several new trigonometrical functions.
987 _ Toltec conquerors of the Central American Mayan city of Chichén Itzá construct monuments with ritual astronomical alignments to the rising and setting of the Sun and the sacred planet Venus.
1050 _ The astrolabe, a new device for making astronomical measurements and calculations, arrives in Europe from the East, where Muslim scientists developed it two centuries ago.
1054 _ 4 JULY: A bright new star, visible in daylight, appears in the constellation Taurus. The supernova (which forms the Crab Nebula) is observed in China and Korea, and is recorded in rock paintings in southwestern America.
1066 _ The comet later known as Halley's Comet appears in the sky, and is taken as an omen by both the Norman and English sides before the Battle of Hastings. The victorious Normans record its appearance in the Bayeux Tapestry.
1074 _ The Seljuk sultan Malik Shah of Baghdad builds a new observatory (at Isfahan, Persia), where the astronomer and poet 'Umar al-Khayyam is appointed to reform the old Persian calendar.
1087 _ Al-Zarqellu and other Muslim Andalusian astronomers compile the Toledan Tables, which become known for their accuracy, and are translated more widely than any other Arab astronomical tables.
1091 The Benedictine abbot and monastic reformer Wilhelm of Hirsau writes his astronomical treatise De astronomia/On Astronomy.    The French-born Prior Walcher of Malvern Abbey, England, records his observations in Italy of an eclipse of the moon. This is one of the earliest accurate western European observations of the phenomenon.
1108 _ The French-born Prior Walcher of Malvern Abbey, England, compiles tables mapping the movements of the moon in the period 1036–1112. This is the earliest European attempt at such a difficult astronomical feat.
1145 _ A carving near a sacred lake at the Toltec sacred city of Chichén Itzá records a transit of Venus across the face of the sun, an event of great religious significance.
1178 _ Monks at Canterbury, England, report seeing fire issue from one of the horns of the new moon. It is the only authenticated record of a lunar meteor impact.
1259 _ The Persian philosopher At-Tusi, employed by the Mongol Hulagu Khan, founds an observatory at Maraghah, Persia.
1276 _ The Chinese astronomer Guo Shou-jing builds a 12 m/40 ft tower gnomon (the stationary arm that projects the shadow on a sundial) at Gao Cheng Zhen, China, with a 36 m/120 ft horizontal stone scale for measuring the length of its shadow at midday. He is thus able to maintain a calendar.
1290 _ The French astronomer William of St-Cloud obtains an accurate measurement of the obliquity of the ecliptic (the angle of the sun's apparent path around the sky) at Paris, France.
1293 _ The Danish astronomer Peter Nightingale develops an equatorium, an astronomical model for use in calculating and predicting eclipses.
1318 _ 13 MARCH: The French astronomer Jean de Murs determines the epoch of the spring equinox using the Spanish Alfonsine Tables. He also writes an explanatory treatise responsible for increasing the use of the tables in the rest of Europe.
1342 _ The work of the French-born Hebrew astronomer Levi ben Gerson (Gersonides) is translated into Latin as De sinibus, chordis et arcubus/Concerning Sines, Chords and Arcs, a treatise on trigonometry introducing the use of the cross-staff for astronomical observations.
1350 _ French astrologer Jean de Linières compiles a catalog of stars.
1364 _ The French astronomer and bishop Nicole d'Oresme writes Latitudes of Forms, an early work on coordinate systems.
1377 _ The French astronomer and bishop Nicole d'Oresme writes a commentary on Aristotle's De caelo/Concerning the Heavens, suggesting a heliocentric theory of the universe, and even that there might be 'more than one universe'.
1391 _ The English writer Geoffrey Chaucer writes A Treatise on the Astrolabe in Middle English.
1424 _ Mongolian ruler and astronomer Ulugh Beg, Prince of Samarkand, builds a great observatory, including a 40 m/132 ft sextant, which enables extremely accurate measurements to be made, cataloguing over 1,000 stars.
1437 _ Astronomers of Samarkand make the Tables of Ulugh Beg for the city's ruler, the Mongol mathematician and astronomer Ulugh Beg; they correct several errors made in the works of Ptolemy.
1454 _ The Austrian astronomer Georg Peurbach completes his New Theory of the Planets, supporting the 'sphere' model of the universe, and using new observations to improve the measurement of celestial distances.
1457 _ Hebrew astronomer Judah Verga of Lisbon writes a description of his invention for determining the Sun's meridian.
1472 _ Halley's comet passes close to Earth, appearing as a brilliant 'Great Comet', and inspiring a wave of superstition.
1473 _ The Jewish astronomer Abraham Zacuto of Salamanca, Spain, begins five years of observations to determine accurately the Sun's changing declination from day to day.
1475 _ German astronomer Regiomontanus publishes De triangulis planis et sphaericis/Concerning Plane and Spherical Triangles, a book on spherical trigonometry as applied to astronomy.
1514 _ The Polish astronomer and priest Nicholas Copernicus writes a short pamphlet on the problems of the Aristotelian Earth-centerd view of the universe, the Commentariolus/Brief Commentary, and circulates it privately.
1519 _ The Spanish conquistador Hernán Cortés sends the Mayan 'Dresden Codex' to Charles V of Spain—it demonstrates the elaborate Mayan calendar based on the movements of the planet Venus.
1530 _ Belgian mathematician and cosmographer Gemma Frisius suggests that longitude can be calculated by the difference in time as measured by the Sun at two places.
1533 _ The Polish astronomer and priest Nicholas Copernicus lectures in Rome on the idea of a Sun-centerd (heliocentric) universe, with the approval of Pope Clement VII, who attends some of his lectures.
1538 _ The Italian astronomer and physician Girolamo Fracastoro publishes his discovery that the tails of comets always point away from the Sun.
1540 _ The German astronomer Georg Rhaticus persuades the Polish astronomer and priest Nicholas Copernicus to publish his Commentariolus/Brief Commentary on the heliocentric system of the universe. The printer, however, inserts a preface suggesting the idea is only a model for simplifying astronomical calculations.
1542 _ The German Protestant religious reformer Martin Luther attacks the heliocentric universe proposed by Polish astronomer and priest Nicholas Copernicus.
1543 _ Polish astronomer and priest Nicolaus Copernicus publishes De revolutionibus orbium coelestium/On the Revolutions of the Celestial Sphere, detailing his theory that the Earth and other planets orbit the Sun on circular paths. A copy of the book is brought to him on his deathbed.
1549 _ Melanchthon, a Protestant supporter of Martin Luther, renews attacks on the Polish astronomer Nicolaus Copernicus' s heliocentric system of the universe.
1551 _ English mathematician and philosopher Robert Recorde publishes The Castle of Knowledge, an astronomical treatise in which he supports the Copernican heliocentric theory of the universe.
1563 _ The Danish astronomer Tycho Brahe observes a conjunction of the planets Jupiter and Saturn, one month earlier than predicted by available tables. He sets about producing new, more accurate, tables of his own.
1569 _ While studying at Augsburg, Germany, Danish astronomer Tycho Brahe begins the construction of a 6-m/19-ft quadrant that enables him to plot the positions of celestial objects with unprecedented accuracy.
1572 _ 11 NOVEMBER: The Danish astronomer Tycho Brahe observes a bright new star—a supernova—in the constellation Cassiopeia. It will be known as 'Tycho's Nova'.
1573 _ The Danish astronomer Tycho Brahe publishes his account of his observations of last year's nova in De nova stella/On the New Star.    The German astronomer Michael Mästlin publishes an essay demonstrating that the 'nova' of the previous year was a star, undermining the traditional belief that the stars are unchanging.
1576 _ Danish astronomer Tycho Brahe builds the island observatory of Uraniborg (named for Urania, muse of astronomy) with the finance of King Frederick II of Denmark-Norway.
1577 _ A great comet appears in the skies over Europe, and is observed by many leading astronomers of the day. Danish astronomer Tycho Brahe observes that the parallax of the comet (its movement against the background stars when seen from different positions) is less than that of the Moon, proving that it must be further away, and therefore not an atmospheric phenomena.
1582 _ The German astronomer Michael Mästlin publishes The Epitome of Astronomy, a general introduction to the subject which, depite Mästlin's personal beliefs, still promotes Aristotle's Earth-centerd universe.
1588 Giovanni Paolo Gallucci's Theatrum mundi/Theatre of the World features the first star chart marked with a celestial coordinate system.
1595 _ The German astronomer Johannes Kepler publishes an astrological calendar of predictions at Graz, which proves uncannily accurate.
1596 _ The German astronomer Johannes Kepler publishes his Mysterium Cosmographicum/The Cosmographical Mystery, an attempt to prove that the orbits of the planets around the Sun are all circles contained within a set of nested Pythagorean solids.
1600 _ The Danish astronomer Tycho Brahe meets the German astronomer Johannes Kepler at Prague, and begins to work with him on compiling astronomical tables for the Holy Roman Emperor Rudolph II.
1602 _ Danish astronomer Tycho Brahe's Astronomia instauratae progymnasmata/Introducing Exercises toward a Restored Astronomy is published posthumously, giving accurate positions for 777 fixed stars and a description of the 1572 supernova in Cassiopeia.
1603 _ The German astronomer Johann Bayer publishes his Uranometria star atlas, the most detailed yet, including the 12 new southern constellations, and introducing the practice of giving the stars Greek identifiers.
1604 _ German astronomer Johannes Kepler publishes Astronomiae pars optica/Optical Part of Astronomy, a treatise on optics describing the function of the eye and the way in which light intensity varies with its distance from the source. He also discovers a new star, or 'nova', in the sky, interpreting this as an important astrological omen.    The German Jesuit astronomer Christopher Clavius' Geometrica practica/Practical Geometry is published, detailing the principles of accurate engraving for astronomi cal instruments such as astrolabes.
1606 _ The German astronomer Johannes Kepler publishes his observations of the 1604 nova in the constellation of Ophiuchus in De stella nova in pede Serpentarii/On the New Star in the Serpent-bearer's Foot.
1609 _ German astronomer Johannes Kepler publishes Astronomia nova/New Astronomy, which describes the orbit of Mars accurately. His first two laws of planetary motion state that all planets move in elliptical orbits around the Sun, and that they sweep out equal areas in equal times.    Italian astronomer Galileo Galilei, having obtained a Dutch telescope, makes his own instruments, including one which magnifies objects 32 times. They are the first telescopes that can be used for astronomical observation.    Thomas Harriot of Syon House, near London, England, is the first English astronomer to use a telescope, recording his observations of the Moon.
1610 _ Italian astronomer Galileo Galilei publishes Sidereus nuncius/The Starry Messenger, revealing his telescopic discoveries, including the moons of Jupiter, the phases of Venus, sunspots, and the curious shape of Saturn.    The French astronomer Nicholas Pieresc discovers the Orion Nebula.
7 JANUARY: Italian astronomer Galileo observes three satellites orbiting Jupiter. He names them 'Sidera Medicea', after Cosmo II Medici, Grand Duke of Tuscany. Later he discovers a fourth satellite.
1611 _ English astronomer Thomas Harriott, Dutchman Johannes Fabricius, German priest Christoph Scheiner, and the Italian Galileo Galilei all discover sunspots around the same time. The German astronomer Johannes Kepler publishes his Dioptrice/On Refraction, describing his investigations of light and optics.    The German astronomer Christoph Scheiner uses his telescope to project an image of the Sun onto a white surface, and so is able to observe, sketch, and record the Sun's appearance without damaging his eyesight by direct observation. He suggests that the newly discovered sunspots might be small planets in orbit around the Sun, appearing as dark spots when they transit its face. He soon abandons his theory.    The German astronomer Simon Marius is the first to observe the Andromeda Nebula. He has also discovered the four moons of Jupiter independently of Galileo, and names them Io, Europa, Ganymede, and Callisto.    The Italian astronomer Galileo Galilei's observations of sunspots prove the theory of the German astronomer Johannes Kepler that the Sun rotates.
1612 _ The Italian astronomer Galileo Galilei records that the two 'moons' he believes orbit Saturn have vanished. In fact, he has seen the planet's rings disappear as they lie edge-on to Earth.
1613 _ Convinced by his telescopic observations of the Solar System, the Italian astronomer Galileo Galilei promotes the heliocentric system devised by the Polish astronomer Copernicus.
1615 _ The German astronomer Christoph Scheiner publishes Solellipticus/The Elliptical Sun, drawing attention for the first time to the problem of the Sun's elliptical appearance when on the horizon.
1616 _ The Holy Office in Rome threatens Italian astronomer Galileo Galilei with the severest penalties of the Inquisition unless he agrees not to teach the Copernican system.
1617 _ In his Refractiones caelestes/Celestial Refractions, The German astronomer Christoph Scheiner explains the elliptical appearance of the Sun near the horizon as a result of refraction of its light in the atmosphere.
1618 _ The Swiss astronomer Cysatus of Lucerne is the first person to observe a comet using a telescope.
1619 _ English astronomer John Bainbridge publishes An Astronomical Description of the Comet of 1618, considering the comet as an astronomical phenomenon and an astrological omen.    German astronomer Johannes Kepler publishes Harmonice mundi/The Harmony of Worlds, which contains his third planetary law, relating the mean distance of a planet from the Sun with its orbital period.
1621 _ Dutch mathematician and astronomer Willibrord Snell discovers his law of refraction, relating the angle by which light is refracted at a boundary to the properties of the media it passes between.    The German astronomer Johannes Kepler's The Epitome of the Copernican Astronomer is burnt by the Roman Catholic Church.
1622 _ The Danish astronomer Christian Longomontanus publishes Astronomia Danica/Danish Astronomy, supporting Tycho Brahe's system of the universe, in which the planets orbit the Sun, but the Sun orbits the Earth.
1624 _ Under the new, more liberal Pope Urban VIII, Italian astronomer Galileo Galilei is allowed to discuss the Copernican view of the Solar System impartially in his lectures at Florence.
1626 _ The German astronomer Christoph Scheiner publishes his Rosa ursina sive sol, detailing his observations of the rotation of sunspots, and calculating the Sun's axis of rotation to be tilted 7.5deg from the ecliptic.
1627 _ German astronomer Johannes Kepler completes the 'Rudolphine Tables', begun by his mentor Danish astronomer Tycho Brahe, for Emperor Rudolph II. The tables give accurate positions of 1,005 fixed stars.
1632 _ An observatory is founded at Leiden University in United Netherlands.    Italian astronomer Galileo Galilei publishes Dialogo sopra i due massimi sistemi del mondo/Dialogue Concerning the Two Chief World Systems, renewing his attack on the geocentric view of the universe.
1633 _ 20 SEPTEMBER: Italian astronomer Galileo Galilei is tried before the Inquisition at Rome, forced to retract his Copernican view of the universe, and sentenced to house arrest.
1638 _ Italian astronomer Galileo Galilei investigates the motion of falling bodies and publishes Discorsi e dimostrazioni matematiche intorno a due nove scienze/Discources and Mathematical Discoveries Concerning Two New Sciences.
1639 _ English scientist William Gascoigne invents the micrometer, an improved version of French engineer Pierre Vernier's calliper rule, and uses it on a telescope to measure the distance between stars.
24 NOVEMBER: English curate Jeremiah Horrocks predicts a transit of Venus across the face of the Sun, and is the first person to observe the event since the Greek mathematician and astronomer Theon of Smyrna in 128 CE.
1642 _ The German astronomer Johannes Hevelius observes bright spots on the surface of the Sun, and calls them faculae.
1644 _ The phases of the planet Mercury are observed for the first time by the German astronomer Johannes Hevelius. The phases were predicted by Copernicus in his heliocentric theory of the Solar System.
1647 _ German astronomer Johannes Hevelius first charts the lunar surface accurately in his Selenographia/Moon Map. The work also describes his discovery of the Moon's libration in longitude, and detailed observations of the Sun.
1650 _ The German astronomer Johannes Hevelius builds telescopes in open frameworks with focal lengths in tens of meters, enabling far greater precision in his measurements.    German astronomer and astrologer Maria Cunitz publishes Urania propitia/Kind Urania.
1651 _ The English scientist William Gilbert's book A New Philosophy of Our Sublunar World is published posthumously, proposing theories that the fixed stars are not all at the same distance from Earth, and that magnetism holds the planets in orbit around the Sun.    The Italian astronomer Giovanni Battista Riccioli publishes a map of the Moon, giving many features their modern names for the first time.
1652 _ The Italian-born French astronomer Giovanni Cassini observes a comet from his observatory at Bologna, Italy, and publishes accurate details of its movements.
1653 _ The Italian-born French astronomer Giovanni Cassini constructs a meridian arc for improved observation of the Sun at San Petrino, Italy.
1659 _ The Dutch scientist Christiaan Huygens realises that the strange shape of the planet Saturn is due to a ring surrounding it, and identifies surface features on Mars for the first time.
1662 _ The English astronomer John Flamsteed accurately observes a solar eclipse from his home, and corresponds with several leading astronomers on the subject.
1663 _ The Scottish astronomer and mathematician James Gregory, in his Optica promota/Optics Advanced, describes the form of compact reflecting telescope that bears his name.
1664 _ Jesuit missionary Adam Schall, once director of the Chinese Imperial Board of Astronomy, is sentenced to execution by the emperor after a bitter dispute with a Chinese astronomer.    The Italian-born French astronomer Giovanni Cassini establishes that the planet Jupiter rotates once every nine hours.
1666 _ Italian-born French astronomer Giovanni Cassini determines rotation periods for the planets Jupiter, Mars, and Venus and observes the polar ice caps on Mars.
1667 _ The Observatoire de Paris is founded at the instigation of controller of finances Jean-Baptiste Colbert. In 1671 Italian-born French astronomer Giovanni Cassini accepts Louis XIV's invitation to direct it.
1671 _ French astronomer and geographer Jean Picard publishes Mesure de la terre/Measure of the Earth that gives the most accurate determination of the length of a meridian of latitude since the early Greek measurements. He is among several scientists who take up French clergyman Gabriel Menton's proposal of the meter as a standard measure of distance.    French astronomer Giovanni Cassini discovers Iapetus, a satellite of Saturn. He will also discover Rhea (1672), Tethys, and Dione (1684).
1672 _ Armed with his calculation of the distance to Mars, the Italian-born French astronomer Giovanni Cassini calculates other astronomical distances, including the astronomical unit (the distance between Earth and Sun).    The Italian-born French astronomer Giovanni Cassini and the French astronomer Jean Richer collaborate to measure the distance to Mars at its close approach to Earth, making simultaneous measurements in Paris, France, and Cayenne, French Guiana, and calculating the distance from parallax. The English astronomer John Flamsteed independently uses parallax to calculate the distance.
1675 _ Danish astronomer Ole Römer calculates the speed of light from the delay in the expected eclipses of Jupiter's satellites when the planet is farthest from Earth. He estimates the Sun's rays reach the Earth in 11 minutes.    The Italian-born French astronomer Giovanni Cassini observes a dark division in the ring of Saturn, leading him to suggest the ring is not a solid structure, but could be composed of thousands of tiny satellites, all in independent orbits.
1676 _ English astronomer Edmond Halley journeys to the Atlantic island of St. Helena to map the stars of the southern skies. He is hampered by the poor instruments of the time and the island's weather.
1677 _ The English astronomer Edmond Halley observers a transit of Mercury across the Sun from the Atlantic island of St Helena.
1678 _ The Danish astronomer Ole Römer invents an automatic planetarium for projecting images of the sky.
1679 _ English astronomer Edmond Halley publishes his Catalogus stellarum australium/Catalog of Southern Stars, a result of his surveys from the island of St Helena, giving descriptions of 341 southern stars.    Italian-born French astronomer Giovanni Cassini presents his map of the Moon to the French Academy of Sciences in Pa ris, France. It is the result of eight years work, and the most accurate chart yet published.
1680 _ English physicist Isaac Newton calculates that an inverse-square law of gravitational attraction between the Sun and planets would explain the elliptical orbits discovered by Kepler. He also puts forward a theory that the air resistance encountered by a body increases in proportion to the square of its speed.    The English astronomer John Flamsteed publishes his Doctrine of the Sphere, in which he gives a new, highly accurate determination of the Sun's eccentricity.
1681 _ Inspired by the comet of 1680, the Swiss mathematician and physicist Jacques Bernoulli proposes a theory to explain its nature.
1682 _ French philosopher Pierre Bayle publishes his Thoughts on the Comet of 1680 anonymously, arguing against superstitious beliefs in comets as ill omens.    The English astronomer Edmond Halley observes the comet that he later concludes (in 1705) returns every 76 years, and which now bears his name.
1683 _ The Italian-born French astronomer Giovanni Cassini and the French astronomer N. Fatio publish a study into the phenomenon of zodiacal light, recognizing that it has an astronomical, not meteorological, source.
1684 _ Giovanni Cassini, director of the Observatoire de Paris, publishes Les Eléments de l'astronomie vérifiés/The Elements of Astronomy Verified.
1687 _ The Polish astronomer Johannes Hevelius publishes his Uranographia star atlas, mapping seven new constellations in the northern sky.
1690 _ The Prodromus astronomiae/Introduction to Astronomy, a catalog of over 1,500 stars by Polish astronomer Johannes Hevelius, is posthumously edited and published by his wife Elizabeth Hevelius.    The Dutch astronomer Christiaan Huygens suggests the possibility of life on other planets in the Solar System.
1693 _ English astronomer Edmond Halley compiles tables for calculating the distance of the Sun for navigational purposes.
1698 _ The English astronomer Edmond Halley takes command of the naval sloop Paramour Pink on a voyage to chart magnetic variations at sea, in order to aid navigation.
1700 _ English astronomer Edmond Halley publishes charts showing lines of equal magnetic variations in the Atlantic and Pacific oceans, as an aid to navigation.
1705 _ Berlin Royal Observatory is founded in Germany.    English astronomer Edmond Halley conjectures that a comet seen in 1682 was identical with comets observed in 1607, 1531, and earlier; he correctly predicts its return in 1758. English mathematician and astronomer Isaac Newton is knighted by Queen Anne.
1706 _ Danish astronomer Ole Römer publishes a catalog of observations made at his private Tusculaneum observatory with the first telescope attached to a transit circle.
1710 _ The English astronomer Edmond Halley begins a detailed study of the astronomical works of the Greek scientist Ptolemy (2nd century CE).
1715 _ English astronomer Edmond Halley predicts the path of a total solar eclipse across Britain to a high degree of accuracy.    The French astronomer Joseph-Nicolas Delisle suggests that the Sun's corona, observed during a total solar eclipse, may be caused by the diffraction of light around the Moon.
1718 _ English astronomer Edmond Halley discovers that certain fixed stars have 'proper motions', after having studied the observations of the classical astronomer Ptolemy for several years.
1720 _ English astronomer Edmond Halley succeeds his bitter rival English astronomer John Flamsteed as Astronomer Royal.
1725 _ English instrument maker George Graham graduates a 2.5 m/8 ft mural circle for improved measurements at the Royal Greenwich Observatory in London, England.    The Historia coelest is Britannica/British Study of the Heavens, a mammoth work based on 40 years of observations at Greenwich, England, by English astronomer John Flamsteed, the first Astronomer Royal, is published posthumously.
1728 _ English astronomer James Bradley discovers the aberration of starlight—the difference in the angle at which starlight arrives, depending on whether the Earth is moving away from or towards it.
1729 _ The English astronomer John Flamsteed's Atlas Coelestis/Atlas of the Heavens is published posthumously.
1733 _ The Swedish astronomer Anders Celsius publishes a scientific description of the aurora borealis.
1738 _ French cartographer and astronomer Nicolas de Lacaille makes the first accurate survey of French coastline between Nantes and Bayonne.
1739 _ French cartographer Nicolas de Lacaille leads a survey team measuring a degree of the French meridian between Perpignan and Dunkirk. Their results disprove French astronomer Jacques Cassini's theory that the Earth is flattened at the equator rather than the poles.
1743 _ French astronomer J. N. Delisle devises a method for observing transits of Mercury and Venus by instants of contacts, improving the accuracy of measurements considerably. It will be used widely at the forthcoming transits of Venus in 1761 and 1769.
1745 _ French astronomer Joseph-Nicolas Delisle founds St Petersburg Observatory in Russia.
1748 _ The British Astronomer Royal James Bradley completes a 19-year study of the effect of the Moon's orbit on the Earth, discovering the "nutation" that causes the Earth to wobble in its orbit.
1750 _ French astronomer Nicolas de Lacaille leads a French expedition to the Cape of Good Hope. Over four years, he records 10,000 southern stars, identifies new constellations, and draws up the first list of "nebular stars".    The English astronomer Thomas Wright publishes An Original Theory or New Hypothesis of the Universe, accurately describing the shape of the Galaxy and the Sun's location in it, though ascribing a divine importance to its center.    The German mapmaker Johann Mayer publishes Kosmographische Nachrichten und Sammlungen auf das Jahr 1748/Cosmographical Information and Compilations on the Year 1748, a highly praised collection of astronomical tables.
1752 _ The French astronomer Nicolas de Lacaille, observing at the Cape of Good Hope, southern Africa, collaborates with the French astronomer Joseph de Lalande in Berlin, Germany, to measure the parallaxes of Solar System objects, and calculate the distances of the Moon, Sun, and planets.
1753 _ The German cartographer and astronomer Johann Mayer publishes his Lunar Tables, charting the Moon and its movements to one minute of arc, and also concluding the Moon has no atmosphere.
1755 _ In his Allgemeine Naturgeschichte und Theorie des Himmels/Universal Natural History and Theory of the Heavens, the German philosopher Immanuel Kant proposes a theory for the formation of the Solar System from a primordial nebula, predicts the existence of Uranus, and proposes that our galaxy is just one of many in the universe.    The German mapmaker Johann Mayer installs a 1.8-m/6-ft diameter mural quadrant at his observatory, allowing him to compile stellar charts with high accuracy.
1756 German astronomer Johann Tobias Mayer draws up a catalog of 1,000 zodiacal stars and, by comparing them with Ole Römer's observations published in 1706, deduces the proper motions of 80 stars.
1757 _ Croatian-born Italian astronomer and mathematician Roger Boscovich, in Theoris philosophiae naturalis redacta ad unicam legem virium in natura existentium/Theory of Natural Philosophy Reduced to A Single Law of the Strength Existing in Nature, propounds an atomic theory of matter for the first time in modern Europe.
1759 _ French astronomers Alexis Clairault and Jean Bailly calculate the perihelion (closest point to the Sun) of the orbit of Halley's comet. Observations of the return of the comet verify Newton's laws of motion.    The French astronomer Charles Messier is the first professional to sight the return of a comet with a 76-year orbital period, as predicted by Edmond Halley in 1705.
1760 _ To aid his search for more comets, the French astronomer Charles Messier begins the first catalog of nebulae. It is now known that his catalog included galaxies and star clusters as well as nebulae.
1761 _ Russian poet and scientist Mikhail Vasilyevich Lomonosov deduces that Venus has an atmosphere from watching a transit of the planet across the Sun.
1762 _ English astronomer James Bradley catalogs over 60,000 stars.    French astronomer Nicole-Reine Lepaute calculates the time of an annular solar eclipse, and her tables, which show the eclipse at 15-minute intervals, are widely used by astronomers and navigators around the world.
1772 _ German astronomer Johan Elert Bode publicizes the Titius–Bode law (proposed in 1766 by Johann Titius) which states that the distances to the planets are proportional to the terms of the series 0, 3, 6, 12, 24, ... .
1779 _ German astronomer Heinrich Olbers devises a method of calculating the orbits of comets.
1781 _ 13 MARCH: German-born English astronomer William Herschel discovers the planet Uranus.
1784 _ German-born English astronomer William Herschel discovers clouds on Mars.    The first Cepheid variable star is discovered by English astronomer John Goodricke.
1785 _ German-born English astronomer William Herschel argues in his work On the Construction of the Heavens that the Milky Way galaxy is composed of individual stars and is not some luminous fluid.
1786 _ German-born English astronomer William Herschel's Catalog of Nebulae is published. It is a catalog of nearly 2,500 nebulae.
1788 _ French astronomer and mathematician Pierre-Simon Laplace publishes his laws of the Solar System, demonstrating that planetary orbits are stable.
1789 _ German-born English astronomer William Herschel completes his reflecting telescope (the world's largest to date, with a 122 cm/48 in lens), and discovers a seventh satellite (Mimas) in the Saturnian system.
1790 _ 13 NOVEMBER: German-born English astronomer William Herschel discovers a nebulae which he describes as a central star surrounded by a 'luminous fluid'. This contradicts his earlier views and he later concludes that the star was condensing out of a surrounding cloud.
1794 _ German physicist Ernst Florens Friedrich Chladni suggests that meteorites have an extraterrestrial origin.
1796 _ French astronomer Pierre-Simon Laplace, in Exposition du système du monde/Account of the System of the World, enunciates the 'nebular hypothesis', that the Solar System formed from a cloud of gas; it forms the basis of modern theory.
1798 _ French astronomer Pierre-Simon Laplace predicts the existence of black holes.
1800 _ German-born English astronomer William Herschel discovers the existence of infrared solar rays.
1801 _ The German astronomer Johann Elert Bode, the first cartographer to draw boundaries between adjacent constellations, publishes Uranographia, a catalog of 17,240 stars, which also contains 20 star maps.    The German mathematician Karl Friedrich Gauss calculates the orbit of Ceres, discovered earlier in the year. His technique allows other astronomers to locate it.    MAY: German astronomer Heinrich Olbers discovers the second asteroid, Pallas. He is convinced that asteroids are the remains of a disintegrated planet lying between Mars and Jupiter.
1 JANUARY: The Italian astr onomer Giuseppe Piazzi discovers the first asteroid, Ceres.
1802 _ English astronomer William Herschel discovers that some stars revolve around others, forming binary pairs. He catalogs 848 of them.
1804 _ The German astronomer Karl Harding discovers Juno, the third asteroid to be discovered.
1807 _ The German astronomer Heinrich Olbers discovers the fourth asteroid, Vesta.
1811 The German astronomer Wilhelm Olbers theorizes that pressure from solar radiation always forces the tail of a comet to point away from the Sun.
1817 _ The German astronomer Friedrich Wilhelm Bessel develops the 'Bessel function', a mathematical function that explains the movement of three stellar objects whose gravitational effects influence each other.
1818 _ German astronomer Friedrich Wilhelm Bessel, in Fundamenta Astronomiae/Fundamental Principles of Astronomy, records the positions of 50,000 stars on the basis of James Bradley's observations; it is the most accurate star catalog to date.
1819 _ German astronomer Johann Encke discovers the short-period comet (Encke's comet), which returns every 3.29 years.
1825 _ English astronomer John Herschel invents the actinometer for measuring the Sun's light energy.
1826 _ German astronomer Heinrich Olbers formulates the paradox named after him: why is the night sky dark if there are an infinite number of stars?    The English astronomer John Herschel begins to measure the parallax of stars—the apparent shift in a star's position relative to a neighbor caused by the Earth's revolution around the Sun. He thus conclusively proves that the Earth revolves around the Sun.
1832 _ The German astronomer Wilhelm Olbers predicts the Earth will pass through the tail of Biela's Comet, causing panic in Europe.
1834 _ English astronomer John Herschel, at the Cape of Good Hope, catalogs the locations of 68,948 stars in the southern hemisphere.
1837 _ German astronomer Friedrich Struve publishes Micrometric Measurement of Double Stars, a catalog of over 3,000 binary stars.
1838 _ 11 OCTOBER: Using the method of parallax, German astronomer Friedrich Bessel calculates the star 61 Cygni to be 10.3 light years away from Earth. It is the first determination of the distance of a star other than the Sun.
1840 _ Harvard College professor William Cranch Bond erects the first astronomical observatory in the U.S..    The German astronomer Friedrich Bessel explains the irregularities in the orbit of Uranus as due to the gravitational effects of an unknown planet (later identified as Neptune).    U.S. astronomer John William Draper takes the first photograph of the Moon.
1841 _ The German astronomer Friedrich Bessel deduces the elliptical distortion of the Earth—the amount it departs from a perfect sphere—to be 1/299.
1842 _ The German astronomer Friedrich Bessel accurately explains that the wavy course of Sirius is due to the existence of a companion star—the first binary star to be discovered.    Irish astronomer William Parsons Rosse builds the 180-cm/72-in reflecting telescope Leviathan. Used to observe nebulae, its size is not exceeded until the 250-cm/100-in Mount Wilson Observatory telescope is built in 1917.
1843 _ The German astronomer Samuel Heinrich Schwabe discovers that sunspots and the effects of solar disturbances have a cycle of about 11 years.
1846 _ OCTOBER: The British astronomer William Lasell discovers Triton, one of Neptune's two moons—only a month after the planet itself is discovered.
23 SEPTEMBER: German astronomer Johann Gottfried Galle discovers the planet Neptune on the basis of French astronomer Urbain Le Verrier's calculations of its position.
1851 _ The British astronomer William Lasell discovers Arie l and Umbriel, two satellites of Uranus.
1852 _ Irish astronomer Edward Sabine demonstrates a link between sunspot activity and disturbances in the Earth's magnetic field.
1854 _ English astronomer George Biddell Airy calculates the mass of the Earth by swinging a pendulum at the top and bottom of a deep coal mine and measuring the different gravitational effects on it.
1855 _ Irish astronomer William Parsons observes the spiral structure of some galaxies including the Crab Nebulae, and the Great Nebula in Orion.    The English astronomer John Russell Hind discovers the first dwarf nova, U Geminorum. The star brightens by a factor of nearly 40 in a matter of a days before returning to its normal brightness.
1859 _ The German astronomer Friedrich Argelander publishes Bonner Durchmusterung/Bonn Survey, a star catalog listing over 324,000 stars and their magnitudes in the northern hemisphere.
1860 _ By observing sunspots, the English astronomer Richard Carrington discovers that the Sun rotates faster at the equator than at the poles.
1862 _ The English astronomer Warren de la Rue takes stereoscopic photographs of the Sun and Moon.    Scottish-born German astronomer Johann von Lamont discovers the electrical current within the Earth's crust.    The U.S. astronomer Alvan Clark observes the companion star of Sirius—the first white dwarf to be discovered.
1863 English astronomer William Huggins uses the spectra of stars to show that they are composed of the same elements that exist on the Earth and the Sun.
1864 _ By examining their spectra, English astronomer William Huggins demonstrates that the Orion Nebula (and hence all nebulae) consists of gases, while the Andromeda Nebula is composed of stars and is therefore a galaxy.
1865 _ Maria Mitchell of Massachusetts becomes the first woman professor of astronomy when she receives an appointment to Vassar College in Poughkeepsie, New York.
1868 _ The English astronomer Norman Lockyer and the French astronomer Pierre-Jules Janssen announce, independently, a method of spectroscopically observing solar prominences without waiting for an eclipse to block out the Sun's glare.    The English astronomer Norman Lockyer and, independently, the French astronomer Pierre-Jules Janssen, discover helium (element no. 2) through spectroscopic observations of the Sun.    The English astronomer Norman Lockyer discovers that solar prominences are due to an upheaval in the outer layer of the Sun called the chromosphere.
1871 _ The Italian astronomer Giovanni Schiaparelli observes a network of lines on Mars which he calls canali (channels). The word is mistakenly translated as "canals" and leads to widespread speculation that they were constructed by intelligent beings.
1872 _ The U.S. astronomer Henry Draper develops astronomical spectral photography and takes the first photograph of the spectrum of a star—that of Vega.
1874 _ The U.S. astronomer Henry Draper photographs the transit of Venus.
1877 _ 8 AUGUST: U.S. astronomer Asaph Hall discovers Deimos and Phobos, the two moons of Mars.
1880 _ The U.S. astronomer Henry Draper photographs the Orion Nebula, the first photograph of a nebula.
1881 _ U.S. astronomer Edward Emerson Barnard is the first to discover a comet using photography.
24 JUNE: English astronomer William Huggins and U.S. astronomer Henry Draper take the first photograph of the spectrum of a comet.
1885 _ British astronomer David Gill photographs over 450,000 stars of 11th magnitude or brighter in the southern hemisphere, in South Africa. The plates are catalogd by Dutch astronomer Jacobus Cornelius Kapteyn to produce the Cape Photographic Durchmusterung star catalog in 1900.
1887 _ The Paris Obs ervatory in France enlists 18 observatories around the world to make a photographic map of 10 million stars, and to catalog all stars of 12th magnitude or brighter. The map, known as the Carte du ciel, is still incomplete, but the catalog is completed in 1958.
1888 _ British astronomer Joseph Norman Lockyer describes the evolution of a star from birth to extinction.    Danish astronomer Ludvig Emil Dreyer publishes the New General Catalog of Nebulae and Clusters of Stars, which lists over 8,000 nebulae. This number is increased to 13,000 by 1895; stellar objects are known by their catalog designations, such as NGC1898.    U.S. physicist Henry Augustus Rowland publishes Photographic Map of the Normal Solar Spectrum, an 11 m/35 ft long spectrogram of the Sun, which serves as a standard reference for astronomers.
1889 _ Italian astronomer Giovanni Schiaparelli determines that both Mercury and Venus rotate on their axes and circle the Sun at the same rate so that one side of each planet always faces the Sun.    U.S. astronomer Edward Emerson Barnard takes the first photograph of the Milky Way.
1890 _ The first version of the Henry Draper Star Catalog is published. Produced by astronomers at Harvard College Observatory, it lists the position, magnitude, and type of over 10,000 stars, and begins the alphabetical system of naming stars according to temperature. Subsequent editions increase the listing to 400,000 stars.
1891 _ The "blink" comparator is invented. It permits the discovery of objects in the solar system by comparison of two photographs, taken a few hours apart, of the same region of the sky. Stars remain fixed, while planets and asteroids move or "blink."
1892 _ U.S. astronomer Edward Emerson Barnard discovers Jupiter's fifth moon, Amalthea.
1 FEBRUARY: Auriga, a new star, is observed in the Milky Way.
1895 _ Russian scientist Konstantin Eduardovich Tsiolkovsky publishes Gryozy o zemle i nebe/Dreams of Earth and Sky. The first book about space travel, it discusses the possibility of space flight using liquid-fuelled rockets, and the idea of designing spacecraft with a closed biological cycle to provide oxygen from plants for long flights.
1897 _ U.S. astronomer Alvan Clark completes construction of the 40-inch Yerkes optical refracting telescope in Wisconsin, the largest telescope in the world to date.
1898 _ 13 AUGUST: The asteroid Eros is discovered by German astronomer Gustav Witt.
1899 _ U.S. astronomer William Henry Pickering discovers Phoebe, the ninth satellite of Saturn. He notes that it revolves around Saturn in a retrograde direction.
1903 _ Russian scientist Konstantin Eduardovich Tsiolkovsky writes "Investigations of Space by Means of Rockets," in which he outlines the use of liquid-propelled rockets to escape the Earth's gravity.
1905 _ U.S. astronomer Percival Lowell, after a study of the gravitation of Uranus, predicts the existence of the planet Pluto. Danish astronomer Ejnar Hertzsprung discovers that there is a relationship between the color and absolute brightness of stars and classifies them according to this relationship. The relationship is used to determine the distances of stars and forms the basis of theories of stellar evolution.
1906 _ The asteroid Achilles is discovered by German astronomer Max Wolf. It is the first of approximately 1,000 asteroids known as Trojan planets that form an equilateral triangle with Jupiter and the Sun—an example of the solution to the three-body-problem (the determination of the motion of three bodies under the influence of their natural attraction), it revolves around the Sun in the Lagrangian point of Jupiter's orbit.    U.S. astronomer Percival Lowell publishes Mars and its Canals, in which he argues that the canal-like markings on Mars are irrigation c anals built by intelligent creatures.
1908 _ U.S. astronomer George Ellery Hale discovers that sunspots have magnetic fields.
1909 _ English astronomer John Evershed discovers that gases radiate from the centers of sunspots.
1910 _ 19 MAY: Halley's comet – which comes near the Earth roughly every 75 years—returns, with the Earth passing through the comet's tail. In the U.S., it is regarded by some as announcing the end of the world. "Comet Pills," allegedly an antidote to the poisonous gases thought to be in the comet's tail, also sell well.
1912 _ U.S. astronomer Edward Barnard discovers Barnard's star. Second nearest star to the Sun, it displays the greatest movement of any star relative to others.    U.S. astronomer Henrietta Leavitt establishes a relationship between the period and luminosity of Cepheid variable stars (stars which pulsate and vary regularly in brightness). The relationship is later used to calculate interstellar and intergalactic distances.    U.S. astronomer Vesto Slipher measures the radial velocities of spiral nebulae by examining small changes in the Doppler effect which suggest that they must be external to our galaxy. His work is later built on by U.S. astronomer Edwin Hubble to show that the universe is expanding.
1913 _ Danish astronomer Ejnar Hertzsprung introduces a luminosity scale of Cepheid variable stars to measure their distance.    U.S. astronomer Henry Russell shows that there is a correlation between a star's brightness and its spectrum. The correlation is important in determining stellar distances.
1914 _ British astronomer John Franklin publishes the Franklin-Adams Charts, the first photographic star charts of the entire sky.    English astrophysicist Arthur Eddington publishes Stellar Movement and the Structure of the Universe, in which he theorizes that spiral nebulae are galaxies similar to the Milky Way.
1915 _ Proxima Centauri is discovered. The closest star to the Sun it is 4.2 light years away.
1916 _ German astronomer Karl Schwarzschild offers a solution to Einstein's gravitational field equations which predicts the existence of black holes, collapsed stellar bodies.
1917 _ Dutch astronomer Willem de Sitter shows that Einstein's theory of general relativity implies that the universe must be expanding. The 2.5-m/100-in Hooker reflecting telescope is installed at Mount Wilson Observatory, California. It is the world's largest reflecting telescope to date.    U.S. astronomer Harlow Shapley determines that the Sun is situated about 30,000 light years from the central plane of the Galaxy.
1918 _ U.S. astronomer Harlow Shapley estimates the size of the Milky Way as 45,000 light years.
1919 _ U.S .inventor Robert Hutching Goddard publishes "A Method of Reaching Extreme Altitudes," which outlines the use of rockets as a means to reach the Moon.    The International Astronomical Union (IAU) is founded to promote international cooperation in astronomy.    U.S. astronomer William Pickering predicts the existence and location of the planet Pluto.
29 MAY: English astrophysicist Arthur Eddington and others observe the total eclipse of the Sun on Príncipe Island (West Africa), and discover that the Sun's gravity bends the light from the stars beyond the edge of the eclipsed sun, thus confirming Albert Einstein's theory of relativity.
1920 _ German astronomer Walter Baade discovers the asteroid Hidalgo, which is unusual in that its orbit is tilted out of the plane of the Solar System by 43°.
1922 _ 12 MAY: A 20.3-tonne/20-ton meteorite lands in a field near Blackstone, Virginia, leaving a 46 sq m/500 sq ft hole in the ground.
1924 _ U.S. astronomer Edwin Hubble demonstrates that certain Cepheid variable stars are several hundred thousand ligh t years away and thus outside the Milky Way galaxy. The nebulae they are found in are the first galaxies to be discovered that are proved to be independent of the Milky Way.
1925 _ U.S. inventor Robert Hutchings Goddard conducts a static test of a liquid-propelled rocket.    Swedish astronomer Bertil Lindblad discovers that the Milky Way rotates around its center. One rotation takes 210 million years.    U.S. astronomer Heber Curtis and Swedish astronomer Knut Lundmark contend that spiral nebulae are galaxies similar to the Milky Way.
1926 _ English astrophysicist Arthur Eddington publishes Internal Constitution of the Stars, in which he shows that the luminosity of a star is a function of its mass.
1927 _ The Verein für Raumschiffahrt (Society for Space Travel) is founded in Germany for rocket experimentation.    Belgian astronomer Georges Lemaître proposes that the universe was created by an explosion of energy and matter from a "primaeval atom"—the beginning of the Big Bang theory.    U.S. astronomer Edwin Hubble shows that galaxies are receding and that the further away they are, the faster they are receding.
1928 It is discovered that Neptune's moon Triton rotates in the retrograde direction, that is, opposite that of Neptune's spin.
1929 _ English philosopher Alfred North Whitehead publishes Process and Reality: An Essay in Cosmology.    U.S. astronomer Edwin Hubble publishes Hubble's Law, which states that the ratio of the speed of a galaxy to its distance from Earth is a constant (now known as Hubble's constant).    U.S astronomer Henry Russell publishes "Stellar Evolution," in which he suggests that stars begin as huge cool red bodies, shrink to become hot yellow stars and then hot white and blue dwarfs, and then shrink to become cool red stars.
1930 _ Swiss-born U.S. astronomer Robert Trumpler discovers the existence of interstellar material that reduces the apparent brightness of distant stars.
18 FEBRUARY: U.S. astronomer Clyde Tombaugh, at the Lowell Observatory, Arizona, discovers the ninth planet, Pluto.
1932 _ U.S. engineer Karl Jansky discovers that the interference in telephone communications is caused by radio emissions from the Milky Way. He thus begins the development of radio astronomy.    U.S. scientist Carl David Anderson, while analyzing cosmic rays, discovers positive electrons ("positrons"), the first form of antimatter to be discovered.
1933 _ U.S. astronomer Walter Baade suggests that supernovas develop into neutron stars after exploding.
1937 _ The Austrian astronomer Marietta Blau examines cosmic radiation using a photographic plate.
1940 _ Belgian astronomer Marcel Gilles Jozef Minnaert publishes Photometric Atlas of the Solar Spectrum, a standard reference text providing measurements of the absorption lines from 3,332 angstroms to 8,771 angstroms.
1942 _ Radar operators in the British army detect, for the first time, radio emissions from the Sun.    U.S. radio engineer Grote Reber makes the first radio maps of the sky, locating individual radio sources.
1944 _ The Dutch astronomer Hendrik van de Hulst predicts that cosmic hydrogen will emit line radiation at 21 cm/8.3 in.
1945 _ Hungarian scientist Lajos Jánossy investigates cosmic radiation.    The Hungarian astronomer Zoltán Bay and the U.S. Army Signal Corps Laboratory at Fort Monmouth, New Jersey, receive radar echoes from the Moon.
1948 The U.S. astronomer Gerard Kuiper discovers and photographs Miranda, the fifth moon of Uranus.    The U.S. physicists George Gamow and Ralph Alpher develop the "big bang" theory of the origin of the universe, which says that a primeval explosion led to the universe expanding rapidly from a highly compressed original state.
1949 _ The U.S. astronomer Walter Baade discovers the close approach asteroid Icarus; except for comets, it has the most eccentric orbit of any body in the solar system, and passes closest to the Sun (28 million km/18 million mi).
1950 _ The Dutch astronomer Jan Oort proposes that comets originate in a vast cloud of bodies (the "Oort cloud") that orbits the Sun at a distance of about one light year.
1951 _ 20 SEPTEMBER: The U.S. Air Force makes the first successful recovery of animals from a rocket flight when a monkey and 11 mice are recovered from a flight to an altitude of 72,000 m/236,000 ft.    The U.S. astronomer Gerard Kuiper proposes the existence of a ring of small, icy bodies orbiting the Sun beyond Pluto, thought to be the source of comets. They are discovered in the 1990s and it is named the Kuiper belt.
14 SEPTEMBER: The "close-approach" asteroid Geographos is discovered by astronomers at the Mount Palomar Observatory in California.
1954 _ 21 MAY: The Central Observatory of the Soviet Academy of Sciences, near Leningrad, U.S.S.R, opens.
1955 _ French astronomer Audouin Dolfus ascends 7.2 km/4.5 mi above the Earth in a balloon to make photoelectric observations of Mars.
5 MAY: U.S. astronomer B F Burk announces the discovery that Jupiter emits radio waves.    SEPTEMBER: The National Geographic Society, pointing to blue-green patches in photo
1957 _ The U.S. launches the first Jupiter-C three-stage rocket. It has a recoverable nose cone and is used for the first flights to carry live animals.
19 AUGUST: U.S. astronomers, using a 33 cm/12 in telescope on board the uncrewed balloon-telescope STRATOSCOPE I, take the first clear photographs of the Sun from 24,384 m/80,000 ft.
4 OCTOBER: The U.S.S.R launches the first artificial satellite, Sputnik 1, to study the cosmosphere. It weighs 84 kg/184 lb and circles the Earth in 95 minutes, inaugurating the space age.
3 NOVEMBER–13 APRIL 1958: The Soviet spacecraft Sputnik 2 is placed in orbit carrying a dog, Laika. It is the first vehicle to carry a living organism into orbit. Laika dies in space.
1958 _ Radio astronomers receive the reflection of radio waves from Venus. Similar echoes from other objects in the Solar System allow an accurate measurement of their distance.
31 JANUARY: The U.S. Army launches Explorer 1 into Earth orbit. The first U.S. satellite, it is used to study cosmic rays.
17 MARCH: The U.S. launches Vanguard 1. The second U.S. satellite, it tests solar cells and consists of a 1.47 kg/3.25 lb sphere equipped with two radio transmitters. It proves that the Earth is slightly pear-shaped.
15 MAY: The U.S.S.R places Sputnik 3 in orbit. It contains the first multipurpose space laboratory and transmits data about cosmic rays, the composition of the Earth's atmosphere, and ion concentrations.
29 JULY: The U.S. National Aeronautics and Space Administration (NASA) is created for the research and development of vehicles and activities involved in space exploration.
27 AUGUST: The U.S.S.R launches the satellite Sputnik5 , which carries two dogs to a height of 450 km/279 mi.
11 OCTOBER: The U.S. launches the space probe Pioneer 1 into orbit.    NOVEMBER: The U.S. launches Atlas, from Cape Canaveral, Florida. It is a single stage rocket and has a range of 14,400 km/9,000 mi. It was originally designed as an intercontinental ballistic missile (ICBM).
3 NOVEMBER: Soviet astronomer Nikolai Kozyrev first observes a volcanic eruption on the Moon, a gaseous eruption in the crater Alphonsus.
1959 _ The English astronomer Martin Ryle and colleagues publish the Third Cambridge Catalog, a catalog of radio sources that leads to the discovery of the first quasar.    The U.S. astronomer Harold Babco ck discovers that the Sun periodically reverses its magnetic polarity.
2 JANUARY: The U.S.S.R launches Lunik 1. The first spacecraft to escape Earth's gravity, it passes within 6,400 km/4,000 mi of the Moon.
3 MARCH: The U.S. launches the Moon probe Pioneer 4; it passes within 59,000 km/37,000 mi of the Moon.    APRIL: The U.S. National Aeronautics and Space Administration (NASA) selects a pool of nine military test pilots to compete to be the first U.S. astronaut to orbit the earth.    MAY: The U.S. Army sends two monkeys some 500km/300 mi into space. They are recovered, unharmed, in the Caribbean Sea.
7 AUGUST: The U.S. National Aeronautics and Space Administration (NASA) launches the U.S. space probe Explorer 6. It investigates the Van Allen radiation belt discovered in 1958 by Explorer 1 and takes the first television pictures of Earth's cloud cover. The U.S. launches ten other satellites during the year.
14 SEPTEMBER: The Soviet spacecraft Luna 2 (launched on 12 September) becomes the first spacecraft to strike the Moon.
7 OCTOBER: The Soviet Luna 3 (launched on 4 October) takes the first photographs of the far side of the Moon.
1960 _ There are now 20 artificial satellites in orbit.
11 MARCH: The U.S. launches Pioneer 5 , which relays the first measurements of deep space.    MAY: The U.S. launches Midas 2, a satellite designed to provide early warning of a missile attack.
15 MAY: The U.S.S.R launches Spacecraft I. Weighing 4,540 kg/10,000 lb, it is the first vehicle large enough to contain a human passenger.
12 AUGUST: The U.S. National Aeronautics and Space Administration (NASA) launches Echo I, a 30-m/100-ft aluminum-coated balloon used as a passive communications satellite to reflect radio waves. It remains in orbit for eight years and is a conspicuous object in the night sky.
18 AUGUST: The U.S. satellite Discoverer 14 is launched. A U.S. Air Force C-119 transport plane recovers its capsule in midair over the Pacific.
21 AUGUST: The U.S.S.R safely retrieves Spacecraft II, which has two dog passengers.
1961 _ The Soviet space probe Venera 1 passes within 99,000 km/62,000 mi of Venus but fails to transmit data due to a telemetry failure.    JANUARY: The U.S. sends a second primate, this time a chimpanzee, 249 km/155 mi into space aboard a Project Mercury spacecraft. The chimp is successfully recovered.
12 APRIL: Soviet cosmonaut Yuri Gagarin, in Vostok 1, is the first person to enter space. His flight lasts 108 minutes.
5 MAY: U.S. astronaut Alan Shepard in the Mercury capsule Freedom 7 makes a 14.8-minute single suborbital flight. He is the first U.S. astronaut into space.
21 MAY: U.S. president John F. Kennedy commits the country to "landing a man on the Moon and returning him safely to Earth before this decade is out." Following this he will ask Congress to allocate close to $2 billion for space exploration as part of his pledge.
7 AUGUST: Soviet cosmonaut Gherman Titov, the second cosmonaut to be launched into space, completes 17 orbits in 25.5 hours in Vostok 2, and becomes the first person to spend more than a day in space.
27 OCTOBER: The first two-stage Saturn I rocket is launched. The first rocket specifically designed for space flight, it is used to launch the Apollo spacecraft.
1962 _ Italian astronomers Riccardo Giacconi, Herbert Gursky, Frank Paolini, and Bruno Rossi discover the first astronomical X-ray source—in Scorpio.
26 JANUARY: The U.S. National Aeronautics and Space Administration (NASA) launches Ranger 3, a spacecraft designed to photograph and then explore the lunar surface. But Ranger 3 misses its rendezvous with the moon and ends up in a solar orbit.
20 FEBRUARY: U.S. astronaut John Glenn, in the Mercury capsule Friendship 7, becomes the first U.S. astronaut to orbit the Earth. He makes three orbits .    APRIL: Like its predecessor, Ranger 3, the U.S. National Aeronautics and Space Administration's (NASA) lunar probe Ranger 4 malfunctions, and crashes on the moon.
23 APRIL: U.S. spacecraft Ranger 4 becomes the first U.S. spacecraft to hit the Moon.
26 APRIL: The U.S. and UK launch the Earth satellite Ariel. Designed to study the ionosphere, it is the first international cooperative launch.
26 AUGUST: The first UK satellite Aerial is launched to study cosmic radiation.
26 AUGUST: U.S. space probe Mariner 2 is launched. It makes a flyby of Venus (December 14), passing within 34,000 km/21,000 mi of the planet's surface and takes measurements of temperature and atmospheric density.
1 NOVEMBER: The U.S.S.R launches the Mars I probe to Mars. It flies in the right direction but transmits no data because of a radio failure.
1963 _ The European Launcher Development Organization is formed to develop space-launch vehicles. Its test launch site is in Woomera, Australia.    An international team of astronomers discovers the first quasar (3C 273), an extraordinarily distant object brighter than the largest known galaxy yet with a star-like image.
15 MAY–16 MAY: U.S. astronaut Gordon Cooper, in Faith 7, the last of the Mercury missions, completes a 22-orbit mission in 34 hr 20 min (a record) and then makes a manual landing when his automatic controls fail.
20 MAY: The U.S. launches a satellite, Midas, containing a 20-kg/44-lb belt of copper wires into a 3,000 km/1,865 mi polar orbit. The wires are to serve as a reflective umbrella by which to test-relay radio and microwave signals from coast to coast.
16 JUNE: Soviet cosmonaut Valentina Tereshkova, the first woman in space, is launched into a three-day orbital flight aboard Vostok 6, to study the problem of weightlessness.
1964 _ English astronomer Fred Hoyle and Indian astronomer Jayant Narlikar propound a new theory of gravitation that solves the problem of inertia.
28 JULY: The U.S. spacecraft Ranger 7, is launched from Cape Kennedy (the name by which Cape Canaveral was known 1963–73); it succeeds in obtaining close-up photographs of the Moon's surface before crashing (31 July).
12 OCTOBER–13 OCTOBER: The Soviet Voskhod 1 mission is the first spacecraft to have a crew of three.
28 NOVEMBER: The U.S. launches Mariner 4 to Mars. It will pass within 9,800 km/6,118 mi of the planet on 14 July 1965, and relay the first close-up photographs of the surface, as well as information on the Martian atmosphere.
1965 _ U.S. astronomers Arno Penzias and Robert Wilson detect microwave background radiation in the universe and suggest that it is the residual radiation from the big bang.
18 MARCH: Soviet cosmonaut Alexsi Leonov leaves spacecraft Voskhod 2 and floats in space for 20 minutes—the first space walk.
23 MARCH: U.S. astronauts Virgil Grissom and John Young are launched aboard Gemini 3. It is the first U.S. space mission with a crew of two.
3 JUNE–7 JUNE: U.S. astronaut Edward White, during the Gemini 4 space mission, demonstrates the ability of humans to function in outer space when he makes a 22 minute space walk, the first by a U.S. astronaut. He is also the first to use a personal propulsion pack during the walk.    JULY: The Soviet spacecraft Zond 3 relays close-up photographs of 7.8 million sq km/3 million sq mi of the Moon's surface.
21 AUGUST–29 AUGUST: The U.S. spacecraft Gemini 5 completes 120 orbits in eight days. It is the longest space flight taken to date and demonstrates the ability of humans to adapt to weightlessness.
12 DECEMBER: The U.S. spacecraft Gemini 6 (launched 4 December) comes to within 0.3 m/1 ft of Gemini 7 (launched 5 December). They are the first spacecraft to rendezvous with each other.
16 DECEMBER: The U.S. launches Pioneer 6 into solar orbit. It relays information abou t the solar wind and cosmic rays, and also data on the tail of comet Kohoutek.
1966 _ Astronomers at the U.S. Naval Research Laboratory, Washington, DC, discover powerful X-rays emitted from within the constellation Cygnus.
3 FEBRUARY: Soviet spacecraft Luna 9 (launched 31 January) makes the first soft landing on the Moon and transmits photographs and soil data for three days.
1 MARCH: Soviet probe Venera 3 (launched 16 November 1965) crash-lands on Venus, the first artificial object to land on another planet.
16 MARCH: U.S. astronauts Neil Armstrong and David Scott, aboard Gemini 8, achieve the first link-up of a crewed spacecraft with another object, an Agena rocket.
2 JUNE: The U.S. National Aeronautics and Space Administration (NASA) spacecraft Surveyor I (launched 30 May) makes the first U.S. soft landing on the Moon, and transmits over 10,000 photographs of the lunar surface.
10 AUGUST: The U.S. spacecraft Lunar Orbiter 1 enters Moon orbit and transmits pictures of the dark side. It is the first of a series of five uncrewed spacecraft that photograph the Moon to select sites for the Apollo missions and to make detailed lunar maps.
11 NOVEMBER: Gemini 12, the last of the Gemini two-person space missions, is launched. It makes the first fully automatically controlled re-entry.
1967 _ 27 JANUARY: Three U.S. astronauts, Virgil ('Gus') I Grissom, Edward White, and Roger B Chaffee, die in a fire during a countdown rehearsal on the Apollo 1 spacecraft at Cape Kennedy, Florida. They are the first human casualties of the U.S. space program.
17 APRIL: The U.S. spacecraft Surveyor 3 is launched and soft lands on the Moon where it conducts sampling experiments on the lunar soil. It is subsequently visited by astronauts from the Apollo 12 mission.
24 APRIL: Soviet cosmonaut Vladimir Komarov dies during the descent of his Soyuz 1 spacecraft when his parachute fails to open properly. He is the first fatality during a spaceflight and the first of the Soviet space program.
7 JULY: Irish astronomer Jocelyn Bell and English astronomer Anthony Hewish, at the Mullard Radio Astronomy Observatory, Cambridge, England, discover the first pulsar (announced in 1968). A new class of stars, they are later shown to be collapsed neutron stars emitting bursts of radio energy. The Crab Nebula supernova remnant is discovered to be a pulsar the following year.
8 SEPTEMBER: The U.S. spacecraft Surveyor 5 is launched. It measures the proportions of chemicals in the lunar soil.
18 OCTOBER: The Soviet spacecraft Venera 4 (launched 12 June) lands on Venus. The first soft landing on another planet, its instrument-laden capsule transmits information about Venus' atmosphere.
19 OCTOBER: The U.S. spacecraft Mariner 5 (launched on 14 June) passes within 4,000 km/2,500 mi of the surface of Venus, transmitting data on the planet's atmosphere and magnetic field as it does so.
22 OCTOBER–29 OCTOBER: The Soviet spacecraft Cosmos 186 and Cosmos 188 complete the first automatic docking.
7 NOVEMBER: The U.S. spacecraft Surveyor 6 photographs one area of the Moon then lifts off, repositions itself 2.4 m/8 ft away and resumes photographing. It is the first lift-off from an extraterrestrial body.
9 NOVEMBER: The United States launches first three-stage Saturn V rocket. Weighing more than 3,000 tons, it is used to lift the Apollo missions to the Moon.
1968 _ 12 JUNE: The first radar observations of an asteroid are made when the asteroid Icarus approaches within 6 million km/3.7 million mi of Earth.
14 SEPTEMBER–21 SEPTEMBER: The Soviet spacecraft Zond 5 flies around the Moon and returns to Earth—the first spacecraft to do so.
11 OCTOBER–22 OCTOBER: Apollo 7, the first U.S. Apollo space mission with a crew, tests the Command module used on subsequent flights to the Moon, during 163 orbits of the Earth. The crew make the first TV program in space for viewers on 13 October.
1969 _ The Sacramento Peak Observatory at Sunspot, New Mexico, becomes operational. All the air from its 76-cm/30-in diameter 54.9-m/180-ft long solar telescope has been evacuated to prevent it from overheating.
16 JANUARY: Two cosmonauts aboard Soviet spacecraft Soyuz 5 (launched 15 January) dock and transfer to Soyuz 4 (launched 14 January). Locked together for four hours they form the first experimental space station.    FEBRUARY–MARCH: The U.S. space probe Mariner 6 (launched on 24 February) passes within 3,410 km/2,131 mi of the surface of Mars. Mariner 7 (launched on 27 March) photographs the Martian landscape and makes thermal maps of the planet and analyzes its atmosphere.
3 MARCH–13 MARCH: The U.S. Apollo 9 mission tests the lunar module in Earth orbit.
22 MAY: Two astronauts aboard the U.S. Apollo 10 spacecraft (launched on 18 May) transfer into the Lunar module and descend to within 14.5 km/9 mi of the Moon's surface.    OCTOBER: The Soviet spacecraft Soyuz 6, Soyuz 7, and Soyuz 8 are launched on successive days (11, 12, and 13 October). The crews conduct welding experiments in space.
22 NOVEMBER: The lunar module from the U.S. spacecraft Apollo 12 (launched on 14 November) lands on the Moon in the Ocean of Storms. The crew collects 34 kg/75 lb of Moon rocks, inspects Surveyor 3, which landed nearby 2.5 years earlier, and uses a radioisotope-fuelled generator to power experiments.
1970 _ The Small Astronomy Satellite (SAS) is launched by the U.S.. It catalogs X-ray sources and leads to the development of the High Energy Astronomy Observatory (HEAO).    The Soviet spacecraft Venera 7 transmits information from the surface of Venus.    NASA's Orbiting Astronomical Observatory (launched December 1968) and Orbiting Geophysical Observatory detect hydrogen in the tail of a comet.
11 APRIL–17 APRIL: The U.S. National Aeronautics and Space Administration (NASA) narrowly averts a disaster aboard the moon-bound spaceship Apollo 13, after a canister of liquid oxygen explodes in the command module. The crew of James Lovell, John Swigert, and Fred Haise enter the lunar module, which they use as a 'lifeboat' to return safely to earth.
1 JUNE–19 JUNE: The Soviet spacecraft Soyuz 9 remains in orbit for 18 days establishing an endurance record.
12 SEPTEMBER–21 SEPTEMBER: The Soviet uncrewed spacecraft Luna 16 lands on the Moon, collects soil samples in a sealed container, and returns to Earth.    NOVEMBER: The Soviet spacecraft Luna 17 (launched 10 November) lands on the Moon and deploys the remotely-controlled roving Moon vehicle Lunokhod 1.
1971 _ 31 JANUARY–8 FEBRUARY: The U.S. National Aeronautics and Space Administration (NASA) launches the U.S. spaceship Apollo 14 (31 January). Under the command of the U.S. astronaut Alan B Shepard, it reaches the Moon on 5 February and returns to Earth three days later having collected 43 kg/95 lb of lunar rock.
19 APRIL: The U.S.S.R launches the 15-m/50-ft-long Salyut 1 space station. Visited by a three-person crew 7–29 June, the cosmonauts die during their return to Earth when a faulty valve causes their capsule to lose pressure. The station re-enters the Earth's atmosphere six months later.
8 MAY: The U.S. National Aeronautics and Space Administration (NASA) uncrewed spacecraft Mariner 8 plummets into the Atlantic Ocean after the failure of a booster rocket.
26 JULY–7 AUGUST: The U.S. National Aeronautics and Space Administration (NASA) spaceship Apollo 15, commanded by the U.S. astronaut David R Scott, is sent to the Moon. It contains a Lunar Roving Vehicle that enables Scott and his fellow crewman James B Irwin to explore 27 km/17 mi of the lunar surface.
24 NOVEMBER: The U.S. space probe Mariner 9 (launched in May) becomes the first artificial object to orbit anot her planet (Mars); it transmits 7,329 photographs of the planet and its two moons, Deimos and Phobos.
27 NOVEMBER: The Soviet craft Mars 2 (launched 19 May) crashes on Mars returning no data.    DECEMBER: Scientists designate the binary X-ray star system Cygnus X-1 as the first probable black hole.
2 DECEMBER: A capsule from Mars 3 (launched 28 May) successfully lands on Mars but its transmitters go dead after 20 seconds.
1972 _ 5 JANUARY: U.S. president Richard Nixon authorizes a $5.5 billion six-year program to develop plans for a spaceship capable of undertaking multiple missions, thereby launching the space shuttle program.
2 MARCH: The U.S. National Aeronautics and Space Administration (NASA) uncrewed spacecraft Pioneer 10 takes off toward Jupiter.
16 APRIL–27 APRIL: The U.S. launches the Apollo 16 Moon mission; astronauts Charles Duke and John Young return with 97 kg/214 lb of lunar soil and rock after spending a record 71 hr 2 min on the Moon.
22 JULY: The Soviet craft Venera 8 (launched 27 March) makes a soft landing on Venus and transmits valuable data from the surface.
23 JULY: The U.S. launches Landsat 1, the first of a series of satellites for surveying the Earth's resources from space.
7 DECEMBER–19 DECEMBER: Apollo 17 is launched, commanded by U.S. astronaut Eugene Cernan—the last crewed mission to the Moon.
1973 _ Comet Kohoutek is first observed by Czech astronomer Lubos Kohoutek.
6 APRIL: The uncrewed U.S. spacecraft Pioneer 11 rockets toward Jupiter.    MAY: The U.S. National Aeronautics and Space Administration (NASA) launches Skylab, the first U.S. space station. It contains a workshop for carrying out experiments in weightlessness, an observatory for monitoring the Sun, and cameras for photographing the Earth's surface. Skylab is subsequently visited by 3 3-person crews, and astronauts make obsevations of the sun, manufacture superconductors, and conduct other scientific and medical experiments. The third mission (November 1973–February 1974) lasts a record 84 days and gathers data about long space flights.    MAY: The U.S. National Aeronautics and Space Administration (NASA) Skylab 2 transports a team of astronauts on a repair mission to the original U.S. space station Skylab, damaged during its launch on May 14.
28 JULY: Skylab 3 conveys a team of U.S. astronauts to the original Skylab space station, launched on May 14, to make further repairs and conduct experiments.
3 NOVEMBER: The U.S. National Aeronautics and Space Administration (NASA) launches the uncrewed spacecraft Mariner 10, bound for the planet Mercury via Venus.    DECEMBER: The U.S. probe Pioneer 10 (launched 2 March 1972) passes within 130,000 km/81,000 mi of Jupiter taking hundreds of photographs. It is destined to travel beyond the Solar System, leaving it on 13 June 1983.
1974 _ The U.S. probe Mariner 10 (launched 3 November 1973) photographs the upper atmosphere of Venus (February) and then takes the first photographs of the surface of Mercury (March and September), flying within 740 km/460 mi of the planet's surface.    Two Symphonie satellites are launched by France and West Germany, Symphonie A on 12 December 1974 and Symphonie B on 27 August 1975. Placed in geosynchronous orbit over West Africa, they provide Africa with telecommunications services to Western Europe and the Americas.    English radio astronomers Martin Ryle and Antony Hewish receive the Nobel Prize for Physics for their work in radio astronomy.
17 MAY: The U.S. launches the world's first Synchronous Meteorological Satellite (SMS).    SEPTEMBER: U.S. astronomer Charles T Kowal announces the discovery and naming of Leda, the 13th moon of Jupiter.    DECEMBER: U.S. probe Pioneer 11 (launched 6 April 1973) flies to within 42,000 km/26,000 mi of Jupiter and photographs its polar regions.
1975 _ U.S. radio astronomers Russell Hulse and Joseph Taylor identify PSR1913+16 as a binary star (a pair of stars in orbit around each other); it loses energy at a rate that Einstein's theory of general relativity predicts for the emission of gravitational waves (ripples in the structure of spacetime which may occur singly or as continuous radiation).
22 JANUARY: The U.S. launches Landsat 2; it is positioned 180deg from Landsat 1 (launched 23 July 1972). The two together provide regular images of the Earth, including the capability to provide a view of the same geographical area of Earth with the same Sun angle every nine days, which is important in monitoring changes on the surface of the Earth.
15 MARCH: The U.S.-German space probe Helios 1 (launched 10 December 1974) passes the Sun at a distance of 45 million km/28 million mi and returns information about the Sun's magnetic field and solar wind.
15 JULY: The launch of the Soviet spaceship Soyuz 19 signals the start of a joint U.S.–Soviet space mission. U.S. and Soviet astronauts meet in space on July 17 when Soyuz 19 docks with its NASA counterpart, Apollo 18.
16 OCTOBER: The U.S. launches the first Geostationary Operational Environmental Satellite (GOES); it provides 24-hour coverage of U.S. weather.
22 OCTOBER–25 OCTOBER: The Soviet spacecraft Venera 9 and 10, launched on 8 June and 14 June respectively, land on Venus and transmit the first pictures from the surface of another planet.
1976 _ NASA launches three Marisat (Maritime Satellite Systems) satellites; they improve ship-to-shore communications.    The U.S. spacecraft Viking 1 and Viking 2 (launched in 1975) soft-land on Mars (20 July, 7 August). They make meteorological readings of the Martian atmosphere and search for traces of bacterial life which prove inconclusive.    Astronomers at Harvard College Observatory, Cambridge, Massachusetts, discover bursts of X-rays coming from a star cluster 30,000 light years from Earth.
15 JANUARY: The U.S.-German space probe Helios 2 is launched; able to withstand extremely high temperatures, it passes within 43.4 million km/27.0 million mi of the Sun and relays data about cosmic rays, the Sun's magnetic field, and the solar wind.
4 MAY: The U.S. launches Lageos (Laser Geodynamic Satellite); it uses laser beams to make precise measurements of the Earth's movements in an attempt to improve the prediction of earthquakes. Placed in an orbit 9,321 km/5,793 mi high, it is expected to remain in orbit for 8 million years.    JULY: NASA spacecraft Viking I lands on Mars, after an eleven-month voyage. It is joined on Mars by its sister ship Viking 2, which arrives on 7 August.
1977 _ The interplanetary body Chiron is discovered by U.S. astronomer Charles Kowal; at least 200 km/120 mi in diameter, it is initially thought to be an asteroid but is later identified as a giant planetary nucleus.    MARCH: U.S. astronomer James Elliot with several groups of other U.S. astronomers discover rings around Uranus when the planet occludes a relatively bright star.    AUGUST: NASA's space shuttle Enterprise makes its first voyage.
12 AUGUST: The High Energy Astronomy Observatory 1 (HEAO 1) is launched by the U.S. National Aeronautics and Space Administration (NASA). It generates a catalog of X-ray sources.
1978 _ Satellite data begin to be useful in the discovery of new oil deposits.    Miniature nuclear reactors begin to be made to power radar satellites in the U.S.S.R.    The existence of Pluto's satellite Charon is established by U.S. astronomers James Christy and Robert Harrington.
26 JANUARY: The U.S.-European International Ultraviolet Explorer is launched into geostationary orbit; it provides data on ultraviolet sources in outer space.
5 MARCH: The U.S. launches Landsat 3, completing the initial series of land surveying satellites. MAY–9 DECEMBER: NASA launches the spacecraft Pioneer Venus 1, which enters Venus' orbit on 4 December. Pioneer Venus 2, launched on 8 August, probes the planet's surface from 9 December.
15 JUNE–2 NOVEMBER: Two Soviet cosmonauts spend a record 139 days and 14 hours in space.
22 JUNE: U.S. astronomer James W Christy discovers Charon, a moon orbiting Pluto.
27 JUNE: The U.S. satellite Seasat 1 is launched to measure the temperature of sea surfaces, wind and wave movements, ocean currents, and icebergs; it operates for 99 days before its power fails.    DECEMBER: The U.S. space probes Pioneer Venus 1 (launched 20 May 1978) and 2 (launched 8 August 1978), go into orbit around Venus, the first relaying information about the atmosphere, the second taking radar photographs of the surface that reveal huge mountains and basins.
21 DECEMBER–25 DECEMBER: The Soviet spacecraft Venera 11 (launched 9 September 1978) and Venera 12 (launched 14 September 1978) soft land on Venus (Venera 11 on 21 December and 12 on 25 December). They collect data on the lower atmosphere.
1979 _ 25 FEBRUARY–19 AUGUST: Soviet cosmonauts Vladimir Lyakhov and Valeri Ryumin set a new record for time spent in space of 175 days, 36 min.    MARCH: NASA spacecraft Voyager 1 comes within 172,000 miles of Jupiter, in what proves to be its closest approach.    JULY: The U.S. space station Skylab 1 falls back to Earth after travelling 140 million km/87 million mi in orbit since 1973.
1 SEPTEMBER: The U.S. space probe Pioneer 11 (launched 6 April 1973) travels through the rings of Saturn to within 20,900 km/13,000 mi of the planet. The rings are found to be made of ice-covered rocks. Two additional rings and high-energy particles within Saturn's magnetosphere are also discovered.
4 DECEMBER: The European Space Agency's first Ariane rocket is launched from the Guiana Space Center in Kourou, French Guiana; it is designed to deploy satellites into orbit.    The satellite HEAO 2 (High Energy Astronomy Observatory; later renamed the Einstein Observatory, launched 20 September 1979) discovers numerous X-ray sources.    The Soviet space station Salyut 6 (launched 29 September 1977) is the first to be docked by two other spacecraft.    U.S. space probes Voyager 1 (launched 5 September 1977) and 2 (launched 20 August 1977) fly past Jupiter, 1 on 5 March 1979 and 2 on 9 July 1979. Voyager 1 discovers a ring around Jupiter and three moons.    The IRAM array telescope begins operation at Plateau de Bruce, France; its four 15-m/19.2-ft dishes make it the largest millimeter telescope in the world.    The Multiple Mirror Telescope begins operation on Mount Hopkins, Arizona; it focuses the light from six 180-cm/70-in telescopes to form one image, giving the light-gathering power of a single 4.5-m/15.7-ft telescope; it becomes the prototype for larger optical telescopes.    U.S. astronomers John Eddy and Aram Boornazian announce that the Sun is shrinking at a rate of 1.5 m/5 ft per hour.
1980 _ FEBRUARY: NASA launches the Solar Maximum Observatory, designed to examine solar flares.
11 OCTOBER: The Soviet cosmonauts Valery V Ryumin and Leonid I Popov return to Earth after a record 185 days in space aboard Salyut 6.
12 NOVEMBER: The U.S. space probe Voyager 1 flies past Saturn within 124,000 km/77,000 mi; it discovers the planet's 13th, 14th, and 15th moons and transmits information about the planet, its moons, and its rings.    The U.S. Magsat satellite completes its mapping of the Earth's magnetic field.    The U.S. astronomer Carl Sagan publishes Cosmos.    U.S. astronomer Uwe Fink and associates report the discovery of a thin atmosphere on Pluto.    U.S. astrophysicist Alan Guth proposes the theory of the inflationary universe—that the universe expanded very rapidly for a short time after the big bang.
1981 _ AUGUST: T he U.S. probe Voyager 2 records data on the atmospheres of Saturn and its moon Titan.    The most massive star in the universe, R136, is discovered; it is 2,500 times more massive than our Sun and ten times as bright.    The Very Large Array (VLA) radio telescope at Socorro, New Mexico, enters service; its twenty-seven 25-m/82-ft diameter dishes are steerable and moveable on railway tracks and are equivalent to one dish 27 km/17 mi in diameter; together they provide high-resolution radio images.
1982 _ 9 SEPTEMBER: The U.S. rocket Conestoga 1 makes a suborbital flight; it is the first privately operated launch.
11 NOVEMBER: The orbiter Columbia makes the first deployment of a satellite from the U.S. space shuttle.    Astronomers at Villanova University in Pennsylvania, U.S., announce the discovery of rings around Neptune.    Astrophysicists at Groningen University in the Netherlands postulate the existence of a black hole at the center of the Milky Way.
1983 _ 13 JUNE: The U.S. space probe Pioneer 10, launched 3 March 1972) becomes the first artificial object to leave the Solar System.
18 JUNE: Astronauts on board the space shuttle Challenger first use the Remote Manipulating Structure ('arm') to deploy and retrieve a satellite.
18 JUNE–24 JUNE: The U.S. Challenger mission (launched 18 June) includes Sally Ride, the first U.S. woman to go into space.
25 JUNE: The Infrared Astronomical Satellite (IRAS), an orbiting observatory, is launched; it is designed to detect infrared radiation from objects in space and surveys almost the entire infrared sky. It also finds the first evidence of planetary material around the star Vega outside our Solar System.
30 SEPTEMBER: Guion Bluford becomes the first black American to go into space, aboard the U.S. space shuttle.    Studies from the U.S. Lageos satellite (launched 4 May 1976 to monitor slight crustal movements to help predict earthquakes) indicate that the Earth's gravitational field is changing.    The Search for Extraterrestrial Intelligence (SETI) program is established at NASA's Ames Research Center, Mountain View, California.    The Soviet space probes Venera 15 and 16, launched 2 and 7 June 1983, enter orbit around Venus on 10 and 14 October respectively.    The Nobel Prize for Physics is awarded jointly to Indian-born U.S. astrophysicist Subrahmanyan Chandrasekhar and U.S. astrophysicist William Fowler for their studies on the importance of nuclear reactions for the formation of chemical elements in the universe.
1984 _ 18 JULY: Soviet cosmonaut Svetlana Savitskaya becomes the first woman to walk in space.    NOVEMBER: The U.S. National Aeronautics and Space Administration (NASA) astronauts on board the Discovery space shuttle use a Manned Maneuvring Unit (MMU) to retrieve two communications satellites.    The U.S. launches the Earth resource satellite Landsat 4; it uses cameras to view the Earth in several bands of the infrared spectrum.    Astronomers at Cornell University, New York, report the discovery of eight infrared galaxies—thought to resemble primeval galaxies—located by the Infrared Astronomical Satellite.    U.S. astronomers working in Chile photograph a partial ring system around Neptune.
1985    APRIL: NASA invites aerospace firms to compete for the design of an orbiting space station.
27 AUGUST–3 SEPTEMBER: The U.S. space shuttle Discovery (launched 27 August) deploys three satellites; the crew also retrieves, repairs, and redeploys an orbiting satellite.
27 NOVEMBER: The crew of the U.S. space shuttle Atlantis undertakes construction exercises to develop skills for building a large orbiting space station.    European, Japanese, and Soviet probes are launched to rendezvous with Halley's comet in 1986.    The U.S. launches the Earth resource Landsat 5; like Landsat 4 it uses cameras t o view the Earth in several bands of the infrared spectrum.
1986 _ 28 JANUARY: The U.S. space shuttle Challenger explodes shortly after take-off, killing the crew of seven and setting the U.S. space program back years.    JANUARY: The U.S. space probe Voyager 2 passes within 81,000 km/50,600 mi of Uranus; photographs taken by the probe reveal ten unknown satellites and two new rings.
19 FEBRUARY: The U.S.S. R launches the core unit of the Mir 1 space station; it is intended to be permanently occupied.
7 MARCH–17 MARCH: The prime period of the approach to the Sun of Halley's comet. It is visible to the Earth, which occurs roughly every 75 years.    The U.S. space probe Giotto (launched 2 July 1985) reveals that the nucleus of Halley's comet measures 15 km/24 mi by 10 km/16 mi and consists of ices (chiefly water), various gases, and dust particles.    Scientists at Arizona State University conduct computer simulations that strongly suggest that a Mars-sized object struck the Earth a glancing blow about 4.6 billion years ago and was then captured by the Earth; by the end of the year the impact theory is the leading hypothesis about the Moon's origin.
1987 _ 8 FEBRUARY–29 DECEMBER: The Soviet cosmonaut Yuri Romanenko spends a record 326 days in the Mir space station.
23 FEBRUARY: Astronomers around the world observe a spectacular supernova in the Large Magellanic Cloud, the galaxy closest to ours, when a star (SN1987A) suddenly becomes a thousand times brighter than our own Sun. It is the first supernova visible to the naked eye since 1604.    Radio waves are observed from 3C326—believed to be a galaxy in the process of formation.    The U.S.SR launches the Cosmos satellite; it is the 2,000th Soviet satellite.    The U.S.SR's Energiya superbooster is launched—the world's most powerful space launcher with a thrust of 3 million kg/6.6 million lb.    Harvey Butcher , director of the Westerbrook Synthesis Telescope in Groningen, the Netherlands, estimates that the universe is younger than 10 billion years.    Objects the size of planets are found orbiting the stars Gamma Cephei and Epsilon Eridani.    The James Clerk Maxwell Telescope, operated by the Royal Observatory, based in Edinburgh, Scotland, begins operation on Mauna Kea, Hawaii; its 15-m/49-ft dish makes it the largest submillimeter telescope in the world.
1988 _ JULY: Two Soviet Phobos space probes are launched (7 July and 12 July) to study Phobos, one of the moons of Mars; Phobos 1 is accidentally sent a 'suicide' instruction and self-destructs.
19 SEPTEMBER: Horizon, Israel's first satellite, is launched; it is used for geophysical studies.
29 SEPTEMBER–3 OCTOBER: The U.S. space shuttle Discovery makes the first shuttle mission since the Challenger disaster three years previously.
15 NOVEMBER: The Soviet uncrewed space shuttle Buran ('Blizzard') makes its inaugural flight, under radio control.
1989 _ 24 MARCH: The U.S. Delta Star 'Star Wars' satellite is launched; it successfully detects and tracks test missiles shortly after they are launched.
4 MAY: The U.S. space shuttle Atlantis launches the probe Magellan to map the surface of Venus using radar.
8 AUGUST: The European Space Agency's Hipparcos satellite is launched; it carries two telescopes for measuring the distance of stars.
25 AUGUST: The U.S. space probe Voyager 2 (launched 20 August 1989) reaches Neptune and transmits pictures; it discovers a dark spot on the planet and six new moons.
18 OCTOBER: The U.S. space shuttle Atlantis launches the spacecraft Galileo to explore Jupiter. It reaches its destination in December 1995.
18 NOVEMBER: The U.S. Cosmic Background Explorer (COBE) satellite is launched to study microwave background radiation, thought to be a vestige of the big bang.    Astronomers discover a river of gas at the center of the Milky Way, providing further evidence that a black hole, 4 million times as massive as the Sun, exists at the center of our Galaxy.    Star HD 114762 is discovered to have a planet-like body circling it. The Australia Telescope is completed; it has seven 22-m/72-ft dishes and one 64-m/210-ft dish, which are spread throughout New South Wales, Australia, making it one of the largest radio telescopes in the world.    U.S. astronomers J P Huchra and M J Geller discover a large, thin sheet of galaxies, which they name the 'Great Wall'; no current astronomical theory can explain its distinctive form. It is the largest known structure in the universe and is 500 million lightyears long and 200 wide.
1990 _ 24 JANUARY–21 APRIL: Japan launches Muses-A, the first probe to be sent to the Moon since 1976; it places a small satellite in lunar orbit (19 March 1990).    FEBRUARY: The U.S. space probe Voyager 1, now near the edge of the Solar System, turns and takes the first photograph of the entire Solar System from space.
24 APRIL: The space shuttle Discovery places the Hubble Space Telescope in Earth orbit; the main mirror proves to be defective.
1 JUNE: Joint U.S.-German-British Earth-orbiting X-ray observatory Röntgensatellite (ROSAT) is launched; its mission is to study X-rays given off by the coronae of stars.    JULY: U.S. astronomers Juan Uson, Stephen Boughin, and Jeffrey Kuhn announce the discovery of the largest known galaxy; over 1 billion light years away, it has a diameter of 5.6 million light years, almost 80 times that of the Milky Way, and contains about 2 trillion stars.
10 AUGUST: The U.S. Magellan radar mapper arrives in orbit around Venus; it transmits the most detailed pictures of the planet's surface yet produced.
2 DECEMBER–12 DECEMBER: The Soviet spacecraft Soyuz TM-11 is launched, marking the first paying passenger space flight. Japanese newsman Toyuhiro Akiyama, the first Japanese cosmonaut, spends seven days onboard the spacecraft.    U.S. astronomer Mark Showalter discovers an 18th moon of Saturn when analyzing pictures transmitted by Voyager 2.
1991 _ JANUARY: An asteroid 16 km/10 mi in diameter passes between the Moon and the Earth, scoring a near miss.
7 APRIL: The U.S. space shuttle Atlantis launches the Compton Gamma Ray Observatory into Earth orbit to study gamma-rays and their sources. It weighs 16.7 metric tons/17 tons and is the heaviest payload ever carried by a space shuttle.
5 JUNE: The U.S. shuttle Columbia launches the Spacelab Life Sciences-1 laboratory. Astronauts conduct experiments on themselves, rats, and jellyfish polyps.
17 JULY: The European Space Agency's first remote-sensing satellite (ERS-1) is launched into polar orbit to monitor the Earth's temperature from space.
29 OCTOBER: The U.S. spacecraft Galileo takes the closest ever picture of an asteroid—Gaspra—at a distance of 1,600 km/900 mi. The Jodrell Bank radio astronomy center, Cheshire, England, reports the possible discovery of a planet orbiting pulsar star PSR 1829–10.
1992 _ 8 FEBRUARY: The European Space Agency (ESA)/National Aeronautics And Space Administration (NASA) space probe Ulysses flies over the north and south poles of Jupiter to enter a trajectory for reaching the south pole of the Sun; it transmits data about Jupiter's magnetosphere.
5 MAY: The U.S. National Aeronautics and Space Administration (NASA) launches the new shuttle craft Endeavour, named after the 18th-century vessel captained by the English explorer James Cook.
14 MAY: Astronauts on the U.S. space shuttle Endeavour fit a new motor to the Intelsat-6 satellite and fire it into a new orbit.
10 JULY: The European Space Agency's Giotto space probe is diverted to encounter the comet Grigg-Skjellerup.    The Cosmic Background Explorer (COBE) satellite detects ripples in th e microwave background radiation, thought to originate from the formation of galaxies.    The U.S. space probe Magellan maps 99% of the surface of Venus to a resolution of 100 m/330 ft.    The first comet-sized objects in the Kuiper belt are discovered, by U.S. astronomers David Jewitt and Jane Luu, working at Mauna Kea in Hawaii. The U.S. astronomers Jeffrey McClintock, Ronald Remillard, and Charles Bailyn identify Nova Muscae as a black hole approximately 18,000 light years from Earth.
1993 _ MARCH: A star in the galaxy M81, about 11 million light years away from Earth, erupts into a supernova. Archival photographs allow astronomers to study the behavior of the star before it exploded.
21 AUGUST: NASA loses contact with its Mars Observer space probe (cost $980 million).
28 AUGUST: The U.S. spacecraft Galileo discovers the first asteroid moon. About 1.5 km/0.95 mi across and named Dactyl (in 1994), it orbits the asteroid Ida.
7 DECEMBER: The Hubble Space Telescope (placed in Earth orbit in 1990) is repaired and reboosted into a nearly circular orbit by five U.S. astronauts operating from the U.S. space shuttle Endeavour—at a cost of $360 million.    The U.S. astronomers Russell Hulse and Joseph Taylor, Jr, are jointly awarded the Nobel Prize for Physics for their discovery of a new type of pulsar.    U.S. astronomers David Jewitt and Jane Luu discover four large ice objects in the Kuiper belt, a ring of small, icy bodies orbiting the Sun beyond the planets and thought to be the source of comets. The first comet-sized objects in the Kuiper belt were discovered in 1992.    U.S. astronomers identify part of the dark matter in the universe as stray planets and brown dwarfs. Known as MACHOs (massive astrophysical compact halo objects), they may constitute approximately half of the dark matter in the Milky Way's halo.
1994 _ 8 JANUARY: The Russians launch space mission Soyuz-TM 18 with Russian cosmonaut Valeri Polyakov aboard, to their Mir space station. Polyakov plans to spend 14 months at the space station to study the effect on the human body of being in space for the time required to travel to Mars.    FEBRUARY: The Russian cosmonaut Sergei Krikalev flies with the U.S. astronauts Charles Bolden and Kenneth Reightler in the space shuttle Discovery (launched 3 February 1994). He is the first Russian cosmonaut to fly on a U.S. mission in space.
25 JANUARY–10 MAY: The U.S. spacecraft Clementine is launched. The objective of the mission is to make scientific observations of the Moon and the near-Earth asteroid 1620 Geographos. The Clementine discovers an enormous crater on the far side of the Moon. The South Pole-Aitken crater is 2,500 km/1,563 mi across and 13 km/8 mi deep, making it the largest crater in the Solar System discovered so far. It also reveals the possibility of a permanent frozen water-ice deposit in a crater near the south pole of the Moon. On 7 May a malfunction in one of the onboard computers causes the spacecraft to burn up all its fuel and go out of control, making the flyby of Geographos impossible.    MAY: The closest pulsar to the Earth (PSR J0108–1431) is discovered; it is 280 light years away.
16 JULY–22 JULY: Fragments of the comet Shoemaker-Levy 9 collide with Jupiter.
6 DECEMBER: Pictures taken by the Hubble Space Telescope of galaxies in their infancy are published.    DECEMBER: The Apollo asteroid (an asteroid with an orbit that crosses that of Earth) 1994 XM1 passes within 100,000 km/60,000 mi of Earth, the closest observed approach of any asteroid.
1995 _ 9 JANUARY: Russian cosmonaut Valery Poliakov, on board the Mir space station, spends his 366th day in space, breaking the record for the longest stay in space. He returns to Earth on 22 March, after 439 days.
3 FEBRUARY–11 FEBRUARY: NASA's space shuttle Discovery (launched 3 February 1995) is piloted by Ei leen Collins, the first woman to pilot the space shuttle.
22 MARCH: Russian cosmonaut Yelena Kondakova, on the Mir space station, sets a new record for time spent in space by a woman. She returns to Earth after 170 days.    APRIL: The European Space Agency's Earth-sensing satellite ERS-2 is launched successfully. It will work in tandem with ERS-1, launched in 1991, to take measurements of global ozone.
29 JUNE–4 JULY: The U.S. space shuttle Atlantis (launched 29 June) docks with the Russian Mir space station in the first superpower linkup in space since 1975.
23 JULY: U.S. astronomers Alan Hale and Thomas Bopp discover the Hale-Bopp comet. The brightest periodic comet, its icy core is estimated to be 40 km/25 mi wide.    JULY: The Hubble Space Telescope discovers a 320-km/200-mi yellow spot on the surface of Jupiter's moon Io. Although volcanic in origin, its exact cause is unknown.
17 NOVEMBER: The European Space Agency (ESA) launches the Infrared Space Observatory (ISO). Its aim is to discover brown dwarfs (cool masses of gas smaller than the Sun) that make up much of the dark matter of the galaxy.
7 DECEMBER: The U.S. spacecraft Galileo's probe enters Jupiter's atmosphere while Galileo continues to orbit the planet. The probe radios information back about the chemical composition of the atmosphere to the orbiter for 57 minutes before being destroyed by atmospheric pressure.    U.S. astronomers discover the first brown dwarf, an object larger than a planet but not massive enough to ignite into a star, in the constellation Lepus. It is about 20–40 times as massive as Jupiter. Four other brown dwarfs are discovered in 1996. U.S. astronomers also discover water in the sun—in the form of superheated steam—in two sunspots where the temperature is only 3,000°C/ 5,400°F.
1996 _ 30 JANUARY: The comet Hyakutake is discovered by Japanese amateur astronomer Yuji Hyakutake.    JANUARY: The U.S. spacecraft Galileo (launched 18 October 1989) shows less helium on the planet Jupiter than expected. The ratio of helium to hydrogen is similar to that of the Sun, suggesting that the composition of Jupiter has remained unchanged since its formation. The probe also records 700-kph/435-mph winds below one of the cloud layers, suggesting internal heating.    JANUARY: At a meeting of the American Astronomical Society, U.S. astronomers announce the discovery of three new planets orbiting stars, all within 50 light years of Earth. By July 1996 the total number of new planets discovered since October 1995 has risen to ten.
17 FEBRUARY: NASA launches the Near Earth Asteroid Rendezvous (NEAR) space craft towards the asteroid Eros. It will reach the asteroid in February 1999 and will then go into orbit around it and study its size, shape, mass, magnetic field, composition, and surface and internal structure.
26 FEBRUARY: A $442-million satellite is lost in space when its 20 km-/12-mi-long tether, which links the satellite to the shuttle Columbia, snaps. The tethered satellite is designed to generate electricity as it is pulled across the Earth's magnetic field by the shuttle.
24 MARCH: Comet Hyakutake makes its closest approach, passing within 15.4 million km/9.5 million mi of Earth. It is the brightest comet for decades, with a tail extending over 12 degrees of the sky.
25 MARCH: The Russian space station Mir and the U.S. space shuttle Atlantis dock. The U.S. astronaut Shannon Lucid begins a five-month stay aboard Mir.
27 MARCH: Joint U.S.-German-British Röntgensatellite (ROSAT) X-ray astronomy satellite (launched 1 June 1990) records the emission of X-rays from Comet Hyakutake, which are usually associated with a much hotter source.    MARCH: The U.S. spacecraft Galileo detects a magnetic field around Ganymede, suggesting it has a molten core. It also detects molecules containing both carbon and nitrogen, suggesting that life may h ave existed on the moon.    MARCH: The Near Earth Asteroid Tracking (NEAT) system, in its first full month in operation, detects about 200 new asteroids.
4 JUNE: The European Space Agency's Arianespace launches the new Ariane 5 rocket from French Guiana, after ten years of development work. It veers off course immediately after takeoff on its maiden flight and disintegrates (it is blown up for safety reasons), setting the European space program back years.
2 JULY: The U.S. aerospace company Lockheed Martin unveils plans for the X-33, a $1-billion wedge-shaped rocket ship. Called the Venture Star, it will be built and operated by Lockheed Martin and will replace the U.S. space shuttle fleet by the year 2012.
13 AUGUST: NASA scientists report that new images taken by the spacecraft Galileo of Europa, one of Jupiter's moons, show that icy floes on its surface may contain evidence of life.
26 SEPTEMBER: The U.S. astronaut Shannon Lucid ends her 188-day stay in space. It is the longest stay for a U.S. astronaut and the longest for a woman. She has spent most of the time aboard the Russian space station Mir.
3 OCTOBER: British scientists announce meteorite evidence of life on Mars, supporting claims made by NASA and U.S. scientists in August.
7 NOVEMBER: The U.S. National Aeronautics and Space Administration (NASA) launches the Mars Global Surveyor orbiting spacecraft. The objectives of the probe are to study the magnetic field, climate, and composition of the atmosphere of Mars.
16 NOVEMBER: The Russian spacecraft Mars-96 is launched from a site in Kazakhstan, but the booster rockets fail to fire and it falls back to Earth and crashes into the Pacific two days later.
30 NOVEMBER: The 5-km/13-mi-long close-approach asteroid Toutates passes within 5 million km/3 million mi of Earth. Travelling at 140,000 kph/85,0000 mph, it comes close to Earth every four to five years.
3 DECEMBER: The U.S. astronomer Anthony Cook, using data from the satellite Clementine, announces the discovery of a frozen lake at the bottom of a crater on the dark side of the Moon. It would be important for a future Moon colony.
4 DECEMBER: The U.S. National Aeronautics and Space Administration (NASA) launches the Mars Pathfinder. Its main goal is to demonstrate the feasibility of low-cost landings on, and exploration of, Mars. The spacecraft carries a roving machine to explore the surface.
19 DECEMBER: The U.S. Galileo spacecraft flies within 692 km/430 mi of the cracked and icy surface of Jupiter's moon Europa.    Based on data received from the spacecraft Galileo, U.S. astronomers also conclude that Jupiter's moon Io has a metallic core. A 10-megawatt beam of electrons flowing between Jupiter and Io is also detected.    Astronomers announce the discovery of a galaxy in the constellation Virgo, estimated to be 14 billion light years away—the most distant galaxy ever detected. In the same year, astronomers from the Leiden Observatory in the Netherlands and from the Johns Hopkins University in Baltimore, Maryland, U.S., using data from the Hubble Space Telescope, discover a black hole in the galaxy in the constellation Virgo. U.S. geophysicists calculate that the Earth's inner core spins slightly faster than the rest of the planet.
1997 _ The Solar Heliospheric Observatory satellite (SOHO) reveals that Venus's ion-packed tail is 45 million km/28 million mi in length. Discovered in the late 1970s, it stretches away from the Sun and is caused by the bombardment of the ions in Venus's upper atmosphere by the solar wind.    JANUARY: The U.S. Universal Lunarian Society begins offering one-acre sites in the lunar crater Copernicus for $50 with the idea of colonizing the moon. The lunar colony, to be called The City of Lunaria, will consist of 61 zones, each one 1.6 km/1.0 mi in diameter, covered by elliptical domes containing a controlled atmo sphere.
'Sakurai's object', a new star named after the amateur Japanese astronomer who discovered it in 1996 in the constellation of Sagittarius, has expanded since its discovery from an Earth-sized hot dwarf, with a surface temperature of 50,000°C/90,032°F, to a bright yellow supergiant about 80 times wider than the Sun and no hotter than 6,000°C/10,832°F. 'Sakurai's object' may be a red giant star that had previously shrunk, the contraction of its core triggering nuclear reactions and subsequent reinflation.
27 FEBRUARY: The Canadian astronomer David Gray reports that the star 51 Pegasi, thought to have a planet orbiting it, pulsates in precisely the way needed to mimic the signature of a planet in orbit around it. It casts doubt over the presence of other extra-solar planets discovered in the past 18 months.
28 FEBRUARY: The Italian-Dutch satellite BeppoSAX (launched 30 April 1996) observes the first visible-light image of a cosmic gamma-ray burst (GRB)—powerful flashes of gamma rays which occur daily, and randomly, and which outshine all other gamma rays combined. The bursts release more energy in 10 seconds than the Sun will emit in its entire 10-billion-year lifetime, yet no source has ever been observed. The Dutch astronomer Jan van Paradijs and his Italian-Dutch team observe a light source in a distant galaxy that quickly fades after the burst. The bursts were previously thought to be relatively nearby in space.    FEBRUARY: The U.S. spacecraft Galileo (launched 18 October 1989) begins a fly by of Jupiter's moon Europa. It takes photographs of the moon for a potential future landing site.
23 MARCH: The comet Hale–Bopp comes to within 190 million km/1118 million mi of Earth, the closest since 2000 BCE. NASA launches rockets to study the comet. Its icy nucleus is estimated to be 40 km/25 mi wide, making it at least ten times larger than that of Comet Hyakutake and twice the size of Comet Halley.    MARCH: U.S. astronomers announce that the spacecraft Galileo has detected molecules containing carbon and nitrogen on Jupiter's moon Callisto, suggesting that life once existed on the satellite.
28 APRIL: The U.S. astronomer William Purcell announces the discovery of a huge stream of antimatter at the heart of the Milky Way galaxy. The jet, the source of which is a mystery, extends for 3,000 light years above the center of the galaxy.
5 JUNE: The U.S. astronomer Jane Luu and colleagues report the discovery of a new type of object within the solar system – a 'worldlet', known by its catalog number 1996TL66, which has a diameter of 500 km/300 mi and which never gets closer to the Sun than about 35 Astronomical Units (AU, where one AU is equivalent to about 150 million km/93 million mi, the distance between the Earth and Sun). They suggest it represents a new class of object belonging to a population of possibly several thousand orbiting between the Kuiper belt and the Oort cloud.
25 JUNE: During a manually guided docking maneuver the Russian space station Mir collides with its unmanned cargo supply vessel, causing the space station to lose power and oxygen and to tumble out of control. Repairs are subsequently made.
27 JUNE: The U.S. Near Earth Asteroid Rendezvous (NEAR) spacecraft flies within 1,200 km/746 mi of the asteroid Mathilde, taking high-resolution photographs and revealing a 25-km/15.5-mi crater covering the 53-km/33-mi asteroid.
4 JULY: The U.S. spacecraft Mars Pathfinder lands on Mars. Two days later the probe's rover Sojourner, a six-wheeled vehicle that is controlled by an Earth-based operator, begins to explore the area around the spacecraft.
10 JULY: The Japanese astronomer Makoto Hattori and colleagues report the discovery of a knot of mass, which they call a 'dark cluster'. It has the chemical and gravitational properties of a cluster of galaxies, but is optically invisible. A new type of cosmic entity, it helps explain h ow light from a particular quasar has been distorted and challenges the theories of galaxy formation.
1 AUGUST: A study presented at the Division of Planetary Sciences of the American Astronomical Society in Cambridge, Massachusetts, says that the Moon was created early in Earth's history by debris thrown off from Earth after a collision with a planet three times as large as Mars.
7 AUGUST: The space shuttle Discovery blasts off from Cape Canaveral, Florida, on a 12-day ozone research mission to gather environmental data and test new equipment to be used on a future international space station.
7 AUGUST: The U.S. Mars Global Surveyor spacecraft reports the discovery of bacteria on Mars, but later reports there was no bacterial life after all.
12 SEPTEMBER: The U.S. spacecraft Mars Global Surveyor goes into orbit around Mars to conduct a detailed photographic survey of the planet, commencing in March 1998. The spacecraft uses a previously untried technique called 'aerobraking' to turn its initially highly elongated orbit into a 400-km/249-mi circular orbit by dipping into the outer atmosphere of the planet.    OCTOBER: The U.S. National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) launch space probe Cassini to the planet Saturn.
1998 _ 6 JANUARY: The U.S. spacecraft Lunar Prospector is launched to gather information on the Moon's resources, structure, and origin.
8 JANUARY: U.S. astronomers present evidence that the universe will never stop expanding and that it is about 15 billion years old, much older than previous estimates, at a meeting of the American Astronomical Society in Washington, DC.
16 JANUARY: The National Aeronautics and Space Administration (NASA) announces that John Glenn, a Democratic senator from Ohio who became the first American in orbit in 1962, will be part of the space shuttle Discovery team on a ten-day mission to study life sciences. Glenn, who will be 77, will become the oldest space traveller.
24 JANUARY: The U.S. space shuttle Endeavour successfully docks with the Russian space station Mir. U.S. astronaut S. W. Thomas replaces U.S. astronaut David Wolf on the space station.
26 JANUARY: Analysis of high-resolution images from the Galileo spacecraft suggests that the icy crust of Europa, Jupiter's fourth-largest moon, may hide a vast ocean that might be warm enough to support life.
27 JANUARY: Al Schultz of the Space Science Institute in Baltimore, Maryland, using the Hubble Space Telescope, announces the discovery of a giant planet, larger than the Sun, orbiting Proxima Centauri, the closest star to Earth. It is the first planet outside the Solar System to be directly observed.
5 MARCH: U.S. scientists announce that the Lunar Prospector satellite has detected 11 million tonnes of water on the Moon. It is in the form of ice.
11 MARCH: U.S. astronomer Brian Marsden predicts that an asteroid will pass within 48,000 km/30,000 mi of the earth in the year 2028, raising the possibility that it could hit the earth. The following day scientists from the U.S. National Aeronautics and Space Administration (NASA) refute his theory, saying that the asteroid is not likely to come closer than 960,000 km/600,000 mi to the earth.
12 MARCH: Astronomers in Mauna Kea, Hawaii, announce the sighting of a new galaxy, named 0140+326RD1, which is around 90 million light years farther away than the previously known furthest galaxy from Earth.
6 APRIL: The U.S. National Aeronautics and Space Administration (NASA) releases a new picture of a rock formation on Mars. A previous picture made the formation look like a face, fuelling the theory that the formation was constructed by a Martian civilization. The new picture, which does not look like a face, refutes this theory.
2 JULY: U.S. scientists report that the spacecraft Galileo has discovered 12 different vents on J upiter's moon Io which spew lava at temperatures greater than those of any planetary body in the solar system – up to 1,175°C/3,100°F. The temperatures are caused by changes in the moon's shape as it orbits Jupiter.
4 JULY: Astronomers from the University of Hawaii discover the first asteroid entirely within the Earth's orbit; it is 40 m/130 ft in diameter.
4 JULY: Japan's Institute of Space and Astronautical Science launches Planet-B, an uncrewed spacecraft to orbit Mars, from Kagoshima, Japan.
7 JULY: Two Japanese satellites, using sensors and lasers, perform the first automatic docking of a space vehicle.
7 JULY: A Russian nuclear submarine in the Barents Sea launches a commercial satellite into space. The first launch of its kind, it shows that launches can be made from any latitude and that an increased range of orbit can be achieved.
11 JULY: British astronomers in Hawaii discover what they believe to be a solar system forming around the star Epsilon Eridan, ten light years away.
4 SEPTEMBER: U.S. scientist Alan Binder, who is in charge of the uncrewed Lunar Prospector, which is orbiting the Moon, reports that there could be as much as 9 billion tonnes/10 billion tons of ice on the Moon.
29 OCTOBER: U.S. astronaut John Glenn (77) becomes the world's oldest active astronaut, when he blasts off on a nine-day mission on the Discovery space shuttle. His first trip into space was in 1962, when he was the first American to orbit Earth.    OCTOBER: Dutch researchers discover a large galaxy close to our own. The galaxy is 20 million light years away in the Local Void, an area of space that is generally considered to be nearly empty. It escaped detection due to its faintness.
20 NOVEMBER: The spacecraft Zayra, the first module of the £20 billion Alpha International Space Station set up by a group of 16 countries, is launched from Kazakhstan. The station, which is planned for completion in 2004, will orbit the Earth and will house research laboratories and accommodation for seven scientists.
4 DECEMBER: The U.S. space shuttle Endeavour is launched from Cape Canaveral, Florida, to link up the second component of an international space station to Zayra, the first component, which was launched on 20 November.
1999 _ 9 JANUARY: Astronomers from San Francisco State University announce the discovery of three more planets orbiting around neighboring stars, bringing the total number of known planets outside our solar system to 17.
23 JANUARY: NASA scientists photograph light emitted by a gamma ray burst for the first time ever.
6 FEBRUARY: NASA launches the uncrewed spacecraft Stardust from Cape Canaveral, Florida, to collect samples of dust from the comet Wild-2, in the first mission to collect material from beyond the Moon.
1 JUNE: The Russian space agency orders the cosmonauts aboard the Mir space statigraphs of the Martian surface, renews speculation that life exists on Mars.
20 JULY: The X-ray observatory Chandra is placed into orbit during space shuttle mission STS-93. Its goal is to examine exploding stars, black holes, colliding galaxies, and other high-energy cosmic phenomena to help scientists gain a better understanding of the structure and evolution of the universe.    JULY: The National Aeronautics and Space Administration (NASA) crash-lands the spacecraft Lunar Prospector on the Moon, in order to stir up debris that can be analysed for evidence of water vapor.
11 AUGUST: A total solar eclipse occurs in England. The path of the eclipse passes over Cornwall, England—the first total solar eclipse visible there since 1927. Although local businesses have prepared for a large influx of tourists, only a fraction of the expected crowds arrive, and the eclipse is marred by poor visibility due to clouds and rain.
23 SEPTEMBER: The NASA Mars Climate Orbiter crashes into the planet Ma rs due to a navigational error. The spacecraft was launched in December 1999 to study the atmosphere and climate of Mars.
13 OCTOBER: NASA announces that the controlled crash of its Lunar Prospector spacecraft into a crater near the south pole of the Moon on 31 July had produced no observable signature of water.
20 NOVEMBER: China launches its first spacecraft, an uncrewed vehicle that travels for 21 hours in space, from the Jinquan satellite center in the northwest province of Gansu.
2 DECEMBER: The U.S. space probe Mars Polar Lander, launched on 3 January 1999, fails to land on Mars as planned. It was intended to photograph and take samples from the planet.
19 DECEMBER: After repeated delays the space shuttle Discovery launches successfully from the Kennedy Space Center at Cape Canaveral, Florida, on a mission to repair the Hubble space telescope.
2000 _ 18 JANUARY: Richard Cook, the Mars lander project manager at NASA's jet propulsion laboratory, announces that NASA scientists are giving up their search for the Mars Polar Lander which disappeared on 3 December 1999.
11 FEBRUARY–22 FEBRUARY: The space shuttle Endeavour carries out a mission in which it scans the Earth's surface with radar signals to create a detailed topographical map of the world.
25 APRIL: A team of scientists using NASA's Chandra X-ray observatory announce that they have measured the distance to an X-ray source by observing the delay and smearing (filtering) out of X-ray signals traversing 30,000 light years of interstellar gas and dust.
30 APRIL: The spacecraft NEAR Shoemaker, orbiting the near-Earth asteroid 433 Eros, is maneuvered to within 50 km of the surface. Eros is an S-class asteroid approximately 13 × 13 × 33 km in size, the second largest near-Earth asteroid.
4 JUNE: The Compton gamma ray observatory, launched in April 1991, is destroyed by NASA. It outlived its five-year life span by four years.
12 JULY: The launch of the Zvezda service module from Baikonur, Kazakhstan, marks an important milestone in the development of the International Space Station.
11 AUGUST: A Russian Progress cargo ship is launched from the Baikonur Cosmodrome, Kazakhstan, on a Soyuz rocket, carrying clothes, computers, food, and other supplies for use by the first permanent crew of the International Space Station.
31 OCTOBER: One U.S. and two Russian astronauts are launched into space to live in the orbiting International Space Station for the next four months. The station is designed to provide a permanent base in space and to act as a launch pad for planetary exploration.    NOVEMBER: Two teams of astronomers studying the phenomenon of gamma-ray bursts (GRBs) present studies suggesting that GRBs may be created by a massive stellar collapse called a hypernova.
30 DECEMBER: Cassini, an unmanned spacecraft on its way to a Saturn orbit, flys by Jupiter, coming within about 9.7 million kilometers of the planet and sending back photos and other data.    DECEMBER: Astronomers Jerry Larsen and Robert Macmillan separately discover a new TNO (trans-neptunian object), a minor planet or large asteroid in an orbit around the Sun beyond the orbit of Neptune.    DECEMBER: Researchers Michael Malin and Kenneth Edgett announce that images taken by NASA's Mars Global Surveyor appear to show sedimentary rock in outcrops on Mars, which indicates the presence of water on the planet at some time in the past.
2001 _ 12 FEBRUARY: The Near Earth Asteroid Rendezvous mission (NEAR Shoemaker), an unmanned spacecraft launched on Feb 17, 1996, touches down on the surface of asteroid 433 Eros after a year-long orbit. Although the spacecraft was not designed to make a landing, it is unharmed after its descent and continues transmitting images and data for another two weeks before it falls silent.    FEBRUARY: Scientists report that complex carbon molecules o f extraterrestrial origin are found in rocks dating from the boundary between the Permian and the Triassic periods, giving credence to the theory that a mass extinction on Earth 250 million years ago was triggered by a comet or asteroid.
23 MARCH: After 15 years in space (many more than originally planned), Russia's Mir orbital station is deliberately crashed into the Pacific Ocean, disintegrating as it passes through the Earth's atmosphere.    MARCH: A kind of quasar called a type-II quasar, long suspected to exist by scientists, is spotted by Colin Norman of Johns Hopkins University using data from the Very Large Telescope in Chile and from NASA's orbiting Chandra X-ray Observatory.
7 APRIL: NASA's Mars Odyssey orbital probe is launched. Its mission is to gather data, especially information that might indicate the onetime presence of water on Mars, while orbiting the planet for two years
26 APRIL: Astonomers John Bally of the University of Colorado and Henry Throop of the Southwest Research Institute say that observations made with the Hubble Space Telescope reveal large discs of dust around young stars in the Orion Nebula. These clumps of dust may be the first step in the formation of planets.
30 APRIL: A Russian Soyuz spacecraft carrying the first space tourist, US financier Dennis Tito, docks with the International Space Station. Tito pays US$20 million for the privilege.    APRIL: Scientists see the first stages of planet formation in the Orion Nebula.    APRIL: New data from research teams using instruments at the South Pole back the theory that the universe expanded rapidly after the big bang. The scientist's findings of the amount of ordinary matter in the universe matches predictions of this amount based on theories such as Einstein's general theory of relativity.
1 MAY: US president George W Bush confirms plans for the National Missile Defense network (NMD), an ambitious but controversial global anti-missile system, in the face of Russian and Chinese opposition and a lukewarm response from NATO allies.
12 MAY: Alexei Tupolev, leading Russian supersonic aircraft designer, dies in Moscow, Russia (75).
14 JULY: US president Bush's controversial plans to develop a National Missile Defense system receive a boost as an interception test over the Pacific Ocean proves successful.    JULY: The SETI institute adds new optical equipment to their system to search for pulses of light from other star systems. Up till now, SETI has used antennas to scan the skies for radio signals.    JULY: A reanalysis of data from soil samples gathered from Mars by Vikings I and II in the 1970s indicates the presence of life, according to a report by biologist Joseph Miller.
10–12 AUGUST: The yearly Perseid meteor shower occurs when the Earth passes through debris left by the comet Swift-Tuttle.    AUGUST: Using telescopes at the University of California's Lick Observatory, astronomers Geoffrey Marcy and Debra Fischer find a Jupiter-size planet orbiting the star 57 Ursae Majoris in the Big Dipper. This new planet is the second planet found in orbit around the star and proves the existence of planetary systems like ours.    SEPTEMBER: NASA's Deep Space 1 spacecraft, which had its original mission extended in September 1999, flies within 2,200 kilometers of the comet Borrelly, sending back pictures and other data.
1 OCTOBER: Astronomers Barry Turner and A.J. Apponi say they have detected the organic molecule vinyl alcohol in an interstellar dust cloud near the center of the Milky Way galaxy. They used the National Science Foundation's 12 Meter Telescope at Kitt Peak, AZ, to make the significant discovery.    OCTOBER: Astronomers observe the biggest global dust storm on Mars for decades using the Hubble Space Telescope and NASA's Mars Global Surveyor.
13 NOVEMBER: In the course of a summit meeting with Russian president Vladimir P utin, US president Bush announces in Washington, DC, that the USA will cut its nuclear weapons arsenal by two-thirds over the next ten years.
13 DECEMBER: US president George W Bush announces his intention to withdraw from the Anti-Ballistic Missile Treaty with Russia, which has been the cornerstone of nuclear deterrence since 1972.    DECEMBER: Satellite images allow scientists at NASA to create for the first time a map that pinpoints and characterizes lightning strikes across the globe.
2002 _ 1 MARCH: Images of Mars from NASA's Odyssey spacecraft reveal the existence of ice at the planet's south pole.    MAY: Astronomers at the Mauna Kea Observatory in Hawaii announce the discovery in December 2001 of 11 new moons orbiting Jupiter. These are in addition to the 11 satellites found in the summer of 2001, bringing the total to 39.    MAY: The Cosmic Background Imager, a telescope designed by Caltech cosmologists to study microwave background radiation, yields the earliest images of the post-big bang cosmos yet seen.
7 OCTOBER: Astronomers at Caltech announce their discovery of a "miniplanet" beyond Pluto. Called "Quaoar" (officially 2002 LM60), its orbit lies in the Kuiper belt, about 4 billion miles from Earth. "Quaoar" orbits the Sun once every 288 years and is about 1,300 kilometers (about 800 miles) in diameter.
19 DECEMBER: Clouds of methane gas are observed on Saturn's moon Titan, confirming data predicting their existence.
2003 _ 1 FEBRUARY: Space shuttle Columbia disintegrates during re-entry. Astronauts Rick D. Husband, William C. McCool, Michael P. Anderson, David M. Brown, Kalpana Chawla, Laurel Clark, and Ilan Ramon die in the accident.
13 FEBRUARY: The first results from the Wilkinson Microwave Anisotropy Probe (WMAP) are hailed as providing an intimate glimpse into the early years of the universe. WMAP's measurements show that the universe was formed 13.7 billion years ago in the Big Bang, and that the universe will continue expanding forever, laying to rest the "Big Crunch" theory.    FEBRUARY: The Student Dust Collector created by undergraduates is added to the New Horizons mission to Pluto and the Kuiper Belt, set to launch in 2006 or 2007. The students hope that analyzing dust in these remote regions will provide insight into the formation of the solar system.