Astronomy Timeline
Ancient Astronomy: 2800 B.C. to 1600 A.D.
2,800 B.C. – First phase of Stonehenge begins, it is used as a solar/lunar observatory
2,000 B.C. - Egypt and Mesopotamia build first solar/lunar calendars
280 B.C. - Greek astronomer, Aristarchus of Samos shows the Earth revolves around
the Sun
240 B.C. - Greek mathematician Eratosthenes measures the circumference of the
earth
130 B.C. - Greek astronomer Hipparchus develops the first accurate star map and star
catalogue, and a reliable method to predict solar eclipses
46 B.C. - Julius Caesar, after consulting the astronomer Sosigenes of Alexandria,
introduces the Julian Calendar, a regular year of 365 days divided into 12
months, and a leap day is added to February every four years
0 A.D. – Start of the Common Era
140 - Greek astronomer Ptolemy develops geocentric theory of the universe
with Earth at the center
400 – 1200 – Pacific Islanders use constellations to travel across the Pacific Ocean
1050 – Mayan Pyramid of Kukulkan at Chichén Itzá is also used as calendar
1054 - Chinese astronomers observe supernova in Taurus
1120 - First astronomical observatory built in Cairo, Egypt
1259 - Persian astronomer Nasir al-Din al-Tusi builds Iran’s first astronomical
observatory
1420 - Astronomer Ulugh Beg builds astronomical observatory built in
Samarkand, Central Asia
1543 - Polish astronomer Nicolaus Copernicus publishes his heliocentric theory
of the Universe
1572 - Danish astronomer Tycho Brahe discovers a supernova in constellation of
Cassiopeia
1582 - Pope Gregory XIII introduces the Gregorian calendar
Classical Astronomy: 1600 to 1900
1603 German astronomer Johann Bayer publishes his star atlas Uranometria and
introduces the Bayer designation of stars
1608 - Dutch lensmaker Hans Lippershey invents the first practical telescope
1609 - Italian astronomer Galileo Galilei uses telescope to discover four moons of
Jupiter, craters of the moon and the Milky Way Galaxy
1609 - 1619 - German mathematician and astronomer Johannes Kepler
introduces three Laws of Planetary Motion
1610 - Galileo Galilei discovers Saturn’s rings
1656 - Dutch astronomer Christian Huygens discovers Saturn's rings and
the fourth satellite of Saturn Titan
1668 - English mathematician Sir Isaac Newton builds the first reflecting
telescope
1675 - Danish astronomer Ole Romer measures the speed of light
1687 - English mathematician Sir Isaac Newton publishes Principia Mathematica
1705 - British astronomer Edmund Halley predicts the return of the comet
bearing his name
1758 - German astronomer Johann Palitzsch confirms Halley’s 1705 prediction
1781 - Sir William Herschel discovers Uranus
1781 - France’s Charles Messier discovers galaxies, nebula and star clusters
1801 - Italian mathematician and astronomer Giuseppe Piazzi discovers first
asteroid, Ceres
1842 - Austrian mathematician and physicist Christian Doppler publishes his
work on the Doppler Effect
1843 - German astronomer Samuel Heinrich Schwabe describes the sunspot cycle
1846 - German astronomer Johann Galle discovers Neptune
1847 – American astronomer Maria Mitchell becomes the first person to discover a
comet using a telescope
1860-63 - Sir William Huggins uses spectral analysis of stars
1872 - American astronomer Henry Draper takes a first ever photograph of stellar
spectrum using the star Vega
1877 - American astronomer Asaph Hall discovers Martian moons, Phobos and Deimos
Modern Astronomy: 1900 to Present
1905 - Mount Wilson Observatory is built in California
1905 - German Physicist Albert Einstein introduces special Theory of Relativity
1908 - Danish astronomer Ejnar Hertzsprung describes giant and dwarf stars
1908 - American astronomer Henrietta Swan Leavitt discovers Cepheid variables
1916 - German Physicist Albert Einstein introduces his general Theory of Relativity
1923 - American astronomer Edwin Hubble proves other galaxies exist outside the Milky
Way galaxy
1927 - Dutch astronomer Jan Oort calculates the center of the Milky Way Galaxy
1930 - American astronomer Clyde Tombaugh discovers Pluto
1931 - American physicist Karl Jansky discovers cosmic radio waves
1933 - Astrophysicist Fritz Zwicky infers existence of dark matter
1937 - American electrical engineer Grote Reber builds the first radio telescope
1957 - Russians launches man-made satellite Sputnik,
1958 - United States launches first U.S. satellite, Explorer 1
1963 – Quasars are detected
1973 - Astronomers make predictions of Great Attractor
1975 - Vera Rubin announces the existence of dark matter
1986 - Location of Great Attractor is found
1990 - Hubble Space Telescope put into orbit
1994 - Comet Shoemaker-Levy crashes into Jupiter
1999 - Chandra X-ray Observatory is put into orbit
2006 - Dark matter observed separate from ordinary matter
