| A | B |
|---|
| Aristarchus | First proposed heliocentric model |
| Ptolemy | Proposed a geocentric universe |
| Nicolaus Copernicus | "Six Books Concerning the Revolutions of the Heavenly Orbs" |
| Tycho Brahe | Accurate pre-telescopic observations |
| Maria Mitchell | Discovered telescopic comet in 1847 |
| Johannes Kepler | Defined principles of planetary motion |
| Galileo Galilei | Discovered 4 moons orbiting Jupiter |
| William Herschel | Discovered Uranus |
| Isaac Newton | Developed first reflecting telescope |
| Albert Einstein | Speed of light is constant |
| Charles Messier | Wrote catalog of nebulae and star clusters |
| Christianis Hyugens | Discovered Titan, Saturn's largest moon |
| Gian Domenico Cassini | Discovered gap in Saturn's rings |
| Edwin Hubble | Founder of extragalactic astronomy |
| Annie Jump Cannon | Developed star spectra classification scheme |
| Helen Sawyer Hogg | Founded Canadian Astronomical Society |
