5 W H A T I S A S T R O N O M Y ASTRONOMY SPACE Astronomers study all of the objects in the sky outside Earth’s atmosphere Some of the things they study are the sun moons stars planets galaxies asteroids and comets New technologies such as the Hubble Space Telescope help astronomers make new discoveries about outer space The science of astronomy is very old Throughout Earth’s history people have been curious about what they saw in the sky Different ideas developed about how the universe worked A star photographed by the Hubble Space Telescope Dust particles can be seen swirling around the star This drawing shows an 1848 telescope
ASTRONOMY SPACE Key Events in the Early History of Astronomy letters to stars still in use today work Mathematike Syntaxis Nasir al-Din al-Tusi first estimation of Earth-sun distance over 850 of the brightest stars The Julian calendar a purely solar calendar is introduced to the Roman Empire 280 B C Aristarchus thinks the Earth revolves around the sun He provides the 130 B C Hipparchus develops the first accurate star map and star catalogue with 45 B C 140 A D Ptolemy suggests the geocentric theory of the universe in his famous 1259 A D An observatory was built for the famous Persian astronomer 1543 A D Copernicus publishes his heliocentric theory of the universe 1582 A D Pope Gregory XIII introduces the Gregorian calendar 1603 A D Johann Bayer introduces his Bayer designation of stars assigning Greek 1608 A D Hans Lippershey a Dutch spectacles maker invents the telescope 1656 A D Christian Huygens discovers Saturn’s rings and Titan the fourth satellite 1659 A D Huygens notes markings on Mars 1666 A D Martian polar ice caps are noted by Cassini 1668 A D The first reflecting telescope was built by Newton 1675 A D While in Paris Danish astronomer Ole Romer measures the speed 1675 A D Cassini discovers that Saturn’s rings are split into two parts the gap is 1687 A D Newton publishes his theory of gravity This is viewed as the start of 1705 A D England Halley correctly predicts the return of a comet Halley’s comet 1758 A D Johann Palitzsch observes Halley’s comet as predicted by Halley in 1705 1781 A D Herschel discovers the planet Uranus 1781 A D Messier discovers galaxies nebula and star clusters while looking 1801 A D Piazzi discovers the first asteroid Ceres 1840 A D J W Draper takes first pictures of the moon 1846 A D Johann Galle observes and discovers Neptune 1877 A D Asaph Hall discovers Phobos and Deimos the moons of Mars 1877 A D Schiaparelli observes the canals on Mars 1878 A D The Great Red Spot on Jupiter becomes prominent 1905 A D Albert Einstein introduces his special Theory of Relativity 1916 A D Albert Einstein introduces his general Theory of Relativity 1923 A D Hubble shows that galaxies exist outside the Milky Way galaxy 1930 A D Clyde Tombaugh discovers Pluto 1931 A D Karl Jansky discovers cosmic radio waves 1937 A D The first radio telescope is built by Grote Reber Modern Astronomy in 1758 called the Cassini Division of Saturn of light for comets Y M O N O R T S A S I T A H W 6
ASTRONOMY SPACE surface of Venus Robert Harrington Discovery Russians 1957 A D Sputnik the first manmade object to orbit the Earth is launched by the 1958 A D Explorer 1 is launched This was the first U S satellite to orbit the Earth 1960 A D The field of archeoastronomy expands in England 1961 A D Yuri Gagarin becomes the first man in space 1962 A D John Glenn becomes the first American man to orbit Earth 1969 A D Armstrong and Aldrin walk on the moon as part of the Apollo 11 mission 1970 A D The Russian Venera 7 becomes the first spacecraft to land softly on the 1972 A D The U S launches Pioneer 10 the first satellite destined for Jupiter 1974 A D The U S Mariner 10 probe transmits the first image of Mercury 1976 A D The U S Viking probes land on Mars 1977 A D The rings of Uranus are discovered 1978 A D Charon the moon of Pluto is discovered by James Christy and 1980 A D Voyager 1 sends back to Earth the first images of Saturn and its rings 1986 A D Voyager 2 closes in on Uranus 1986 A D The Space Shuttle Challenger breaks apart after launch 1990 A D The Hubble Space Telescope is put into orbit from space shuttle 1992 A D The Vatican under Pope John Paul II announces that the Catholic Church 1994 A D The Comet Shoemaker Levy crashes into Jupiter 1995 A D The Galileo space probe reaches Jupiter 1996 A D The Comet Hyakutake is discovered by Yuji Hyakutake 1997 A D The Mars Pathfinder lands on the Red Planet 1997 A D Cassini begins its journey to Saturn 1998 A D The Lunar Prospector reaches the moon 1998 A D Construction begins on the International Space Station 1998 A D The Galileo space probe discovers the origin of Jupiter’s Rings 1998 A D John Glenn returns to space after 36 years 1999 A D Scientists discover the real Hubble Constant 1999 A D Chandra X-ray Observatory is put into orbit Col Eileen Collins becomes 1999 A D NASA loses the Mars Climate Orbiter and the Mars Polar Lander 2000 A D The space shuttle Endeavor makes a detailed global map of Earth 2000 A D The NEAR spacecraft reaches asteroid Eros 2000 A D New evidence is found for water on Mars 2013 A D NASA’s Voyager 1 spacecraft reached interstellar space 2013 A D Physicists in Antarctica find the first evidence of cosmic rays from 2013 A D NASA’s Curiosity rover discovers signs that ancient Mars could have erred in condemning Galileo’s work that proved that the work of Copernicus was valid mainly that the planets circle the sun and not the Earth the first woman shuttle commander outside the solar system supported life in the form of primitive microbes W H A T I S A S T R O N O M Y 7
8 W H A T I S A S T R O N O M Y ASTRONOMY SPACE Claudius Ptolemaeus c 100 AD c 168 AD is known in English as Ptolemy Views of the Universe Long ago before the invention of the telescope people had a much different idea of what the universe was like The two major views of the universe through the course of history are the geocentric view and the heliocentric view The Geocentric View In 140 A D a Greek astronomer named Ptolemy wrote that the Earth was the center of the universe He thought all the stars the sun and the moon revolved around it This made sense because that is how things looked in the sky from Earth We call Ptolemy’s theory the geocentric view It is derived from geo Earth and centric center Astronomers believed the geocentric view for 1,500 years until 1543 The Heliocentric View About 500 years ago Copernicus found that the Earth and other planets revolve around the sun His theory was published in 1543 We call Copernicus’s theory the heliocentric view because helios means sun Astronomers still base their understanding of the solar system on Copernicus’s heliocentric view Nicolaus Copernicus 1473 1543 Getting to know Nicolaus Copernicus was born in 1473 in what is now Poland His father died when Copernicus was only ten His uncle a Catholic bishop raised him In 1491 he became interested in studying the skies He collected many books on astronomy and studied with famous astronomers In 1513 Copernicus built an observatory He realized that Earth and the other planets revolve around the sun This is the heliocentric view Many people did not believe him The Catholic Church banned his ideas for the next three hundred years We call Copernicus the father of modern astronomy even though Greek Indian and Muslim astronomers before him believed that the sun was the center of the solar system as well
