Nicolaus Copernicus  (1473 -1543) Polish astronomer who first theorized that the Sun, not the Earth, was at the center of the solar system.

 

Galileo Galilei   (1564-1642) Italian astronomer who invented the first telescope used to observe the night sky.

 

Johannes Kepler   (1571-1630) German astronomer best known for his discovery of the three laws of planetary motion.

 

Giovanni Cassini   (1625-1712) French-Italian astronomer known for his discovery of 4 moons and for his detailed observations of the rings of Saturn.

 

Christiaan Huygens   (1629-1695) Dutch astronomer known for his discovery of Saturn's moon, Titan and for his discovery of the composition of the rings of Saturn.

 

Edmund Halley   (1656 - 1742) British astronomer best known for his calculation of the orbit of Halley's Comet which was named in his honor.

 

Charles Messier   (1730 - 1817) French astronomer who compiled a comprehensive catalog of deep-sky objects which is still used today.

 

William Herschel   (1738 - 1822) British astronomer who is best known for his discovery of the planet Uranus in 1781.

 

Johann Bode   (1747-1826) German astronomer best known for Bode's Law, a hypothesis which attempted to explain the behavior of the semi-major axes of planets.

 

George Hale   (1868 - 1938) American astronomer who discovered that sun spots were produced by powerful magnetic fields.

 

Edwin Hubble   (1889-1953) American astronomer who first proposed the theory that the universe is expanding in all directions.

 

James Van Allen   (1914 - 2006) American astronomer whose work on the NASA exploration programs led to the discovery of the Earth's magnetoshphere.

 

Carl Sagan   (1935 - 1996) American astronomer who participated in many of NASA's space exploration programs and helped promote popular science with his PBS series, Cosmos, A Personal Voyage.