2. 83 -161 AD Claudius Ptolemy 83 -161 AD Claudius Ptolemy 1473 -1543 Nicolaus Copernicus 1473 -1543 Nicolaus Copernicus 1564-1642 Galileo Galilei 1564-1642 Galileo Galilei 1571-1630 Johannes Kepler 1571-1630 Johannes Kepler 1625-1712 Giovanni Cassini 1625-1712 Giovanni Cassini 1629-1695 Christiaan Huygens 1629-1695 Christiaan Huygens 1656 - 1742 Edmund Halley 1656 - 1742 Edmund Halley 1730 - 1817 Charles Messier 1730 - 1817 Charles Messier 1738 - 1822 William Herschel 1738 - 1822 William Herschel 1868 - 1938 George Hale 1868 - 1938 George Hale 1889-1953 Edwin Hubble 1889-1953 Edwin Hubble 1914 - 2006 James Van Allen 1914 - 2006 James Van Allen 1935 - 1996 Carl Sagan 1935 - 1996 Carl Sagan

3.  Claudius Ptolemy Claudius Ptolemy (83 AD (est) -161 AD) was an Egyptian scientist and mathematician of Greek descent who is best known for his influential work Almagest, a treatise on mathematics and astronomy published in 150 AD (est). Ptolemy was the most influential of Greek astronomers and geographers of his time. He propounded the geocentric theory that prevailed for 1400 years. Claudius Ptolemy Time line

4.  Nicholaus Copernicus Nicholaus Copernicus (1473-1543), was a Polish astronomer and mathematician who was a proponent of the view of an Earth in daily motion about its axis and in yearly motion around a stationary sun. This theory profoundly altered later workers' view of the universe, but was rejected by the Catholic church. Nicholaus Copernicus Time line

5.  Galileo Galilei Galileo Galilei Galileo Galilei (1564-1642) was an Italian scientist who formulated the basic law of falling bodies, which he verified by careful measurements. He constructed a telescope with which he studied lunar craters, and discovered four moons revolving around Jupiter and espoused the Copernican cause. In 1609, Galileo invented a telescope with a magnification power nearly 10 times greater than that of the primitive telescopes that existed in 16th century Europe. He was the first person to use a telescope to see the planets and stars. This is probably due to the fact that earlier versions of the telescope weren't powerful enough to see anything worthwhile in the sky. Galileo used his telescope to see four of Jupiter's moons, and to see the craters on the Moon in great detail. Time line

6.  Johannes Kepler Johannes Kepler Johannes Kepler was a German mathematician and astronomer who discovered that the Earth and planets travel about the sun in elliptical orbits. He gave three fundamental laws of planetary motion. He also did important work in optics and geometry. Time line

7.  Giovanni Cassini Giovanni Cassini (1625-1712) was a French-Italian astronomer whose observational work in astronomy led a several notable discoveries of objects in the solar system. Cassini is credited with the discovery of Jupiter's Great Red Spot. he was first to observe four of Saturn's moons which he named Sidera Lodoicia. He also discovered the Cassini Divide, plus was the first to observe the differential rotation in Jupiter's atmosphere. He along with a colleague, jean Richer, made simultaneous observations of Mars. These observations lead to the first accurate measurements of the Solar System. Giovanni CassiniSolar System Time line

8.  Christiaan Huygens Christiaan Huygens (1629-1695) was an Dutch scientist and mathematician who is best known for his contributions to mathematics and physics. Christiaan Huygens examined everything in the skies. Using his advanced telescope, he discovered Saturn’s moon which was named Titan. He also studied Saturn’s rings in great detail and later discovered they were made up of rocks. During that same year, Huygens saw and made the first drawing of the Orion Nebula which was in his book Systema Saturnium. He also discovered some double stars and several interstellar nebulae. Huygens was also credited with making the first map of Mars. Christiaan HuygensMars Time line

9.  Edmund Halley Edmund Halley (1656 - 1742) was an English astronomer and physicist who is best known for his prediction of the date of return of the comet which would later become known as Halley's Comet. Halley was known as the comet expert. He could tell when a comet would come and when it would leave. One day Halley saw a comet and claimed that it was a comet that had already been discovered. The next time the comet came Halley proved that theory was true. They named the comet Halley's comet for his discovery. Edmund Halley Time line

10.  Charles Messier Charles Messier (1730 - 1817) was a French Astronomer who is best known for his staggering number of discoveries of astronomical objects. The celebrated French astronomer Charles Messier became famous in his lifetime for the discovery of 20 comets, 13 of which were original discoveries which were (and are still) credited to him. Nowadays, this his devotion is no more appreciated very much, but his fame continues for his Catalog of Nebulae and Star Clusters, which is subject of this database. Charles Messierthis database Time line

11.  William Herschel William Herschel (1738 - 1822) was an English astronomer who is best known for his discoveries of astronomical objects. After constructing the largest reflecting telescope of his era, discovered Uranus, Oberon, and Titania in 1781. He was a patient, careful observer, who visually scanned the entire northern sky. His catalog of extended objects was compiled into the New General Catalog of Nebulae and Clusters of Stars by Dreyer. He constructed a map of the galaxy based of the observed distribution of stars. William Herschel Dreyergalaxystars Timel ine

12.  George Hale George Hale (1868 - 1938) was an American astronomer who is best known for his work in solar astronomy. He was born in Chicago. He was educated at MIT, at the Observatory of Harvard College, (1889-90), and at Berlin (1893-94). As an undergraduate at MIT, he invented the spectroheliograph, with which he made his discoveries of the solar vortices and magnetic fields of sun spots. George HaleChicagoMIT spectroheliographsun spots Time line

13.  Edwin Hubble Edwin Hubble (1889-1953) was an American astronomer who is best known as the namesake of the Hubble Space Telescope. Perhaps more than any other person, Edwin Hubble expanded our view of the universe. Edwin Powell Hubble is renowned for determining that there are other galaxies in the Universe beyond the Milky Way, and for observing that the universe is expanding at a constant rate. Edwin Hubbleother galaxiesuniverse is expanding Time line

14.  James Van Allen James Van Allen (1914 - 2006) was an American astronomer and astrophysicist who is best known for his work with the NASA's early space exploration programs. Van Allen's most influential work occurred during his involvement with the NASA Explorer I and Explorer III missions in 1958.. James Van Allen Time line

15.  Carl Sagan Carl Sagan (1935 - 1996) was an American astronomer and physicist who is best known for his promotion of popular science. American astronomer, author, and popularizer of science and astronomy. Sagan was born in New York City, and received his Ph.D. in astrophysics at the University of Chicago in 1960. Until his death after a long battle with cancer, he was a professor and Director of the Laboratory for Planetary Studies at Cornell University. He is perhaps best known for his creation of the popular public television series Cosmos (1980). Carl Sagan Time line