an Egyptian polymath (born in Iraq) whose research in geometry and optics was influential into the 17th century; established experiments as the norm of proof in physics (died in 1040)

a presocratic Greek philosopher and student of Thales who believed the universal substance to be infinity rather than something resembling ordinary objects (611-547 BC)

an ancient Greek astronomer who was one of the first to propose a heliocentric theory of the universe (circa 270 BC)

German mathematician and astronomer who made accurate measurements of stellar distances and who predicted the existence on an 8th planet (1784-1846)

United States mathematician and astronomer noted for his works on navigation (1773-1838)

Danish astronomer whose observations of the planets provided the basis for Kepler's laws of planetary motion (1546-1601)

Swedish astronomer who devised the centigrade thermometer (1701-1744)

Polish astronomer who produced a workable model of the solar system with the sun in the center (1473-1543)

English astronomer remembered for his popular elucidation of relativity theory (1882-1944)

Greek mathematician and astronomer who estimated the circumference of the earth and the distances to the Moon and sun (276-194 BC)

Italian astronomer and mathematician who was the first to use a telescope to study the stars; demonstrated that different weights descend at the same rate; perfected the refracting telescope that enabled him to make many discoveries (1564-1642)

United States astronomer who discovered that sunspots are associated with strong magnetic fields (1868-1938)

United States astronomer who discovered Phobos and Deimos (the two satellites of Mars) (1829-1907)

English astronomer who used Newton's laws of motion to predict the period of a comet (1656-1742)

English astronomer (born in Germany) who discovered infrared light and who catalogued the stars and discovered the planet Uranus (1738-1822)

English astronomer (son of William Herschel) who extended the catalogue of stars to the southern hemisphere and did pioneering work in photography (1792-1871)

Greek astronomer and mathematician who discovered the precession of the equinoxes and made the first known star chart and is said to have invented trigonometry (second century BC)

English astronomer who pioneered spectroscopic analysis in astronomy and who discovered the red shift (1824-1910)

Greek philosopher and astronomer; she invented the astrolabe (370-415)

German astronomer who first stated laws of planetary motion (1571-1630)

United States astronomer (born in the Netherlands) who studied the solar system and suggested in 1951 that there is a belt of comet-like debris at the edge of the solar system (1905-1973)

United States astronomer and aviation pioneer who invented the bolometer and contributed to the design of early aircraft (1834-1906)

French mathematician and astronomer who formulated the nebular hypothesis concerning the origins of the solar system and who developed the theory of probability (1749-1827)

English astronomer who pioneered radio astronomy (born in 1913)

United States astronomer whose studies of Mars led him to conclude that Mars was inhabited (1855-1916)

United States astronomer who studied sunspots and nebulae (1818-1889)

German mathematician and astronomer (1436-1476)

United States astronomer (1835-1909)

Persian poet and mathematician and astronomer whose poetry was popularized by Edward Fitzgerald's translation (1050-1123)

Dutch astronomer who proved that the galaxy is rotating and proposed the existence of the Oort cloud (1900-1992)

United States mathematician and astronomer remembered for his studies of Uranus and Saturn and Neptune (1809-1880)

Alexandrian astronomer (of the 2nd century) who proposed a geocentric system of astronomy that was undisputed until the late Renaissance

United States astronomer said to have built the first telescope made in America; also the first director of the United States Mint (1732-1796)

United States astronomer who developed a theory of stellar evolution (1877-1957)

Italian astronomer who first noted lines (which he called canals) on the surface of Mars (1835-1910)

United States astronomer (1885-1972)

Dutch astronomer who calculated the size of the universe and suggested that it is expanding (1872-1934)

a presocratic Greek philosopher and astronomer (who predicted an eclipse in 585 BC) who was said by Aristotle to be the founder of physical science; he held that all things originated in water (624-546 BC)

United States astronomer who discovered the planet Pluto (1906-1997)

an English astrophysicist and advocate of the steady state theory of cosmology; described processes of nucleosynthesis inside stars (1915-2001)

United States astronomer who discovered that (as the universe expands) the speed with which nebulae recede increases with their distance from the observer (1889-1953)

Belgian cosmologist who proposed the big-bang theory of the origin of the universe (1894-1966)