Learn about famous astronomers and astrophysicists who have significantly advanced our understanding of the universe, their major discoveries, theories, and contributions to astronomy and astrophysics.  Includes: church opposition to the heliocentric system proposed by Copernicus; astronomer Tycho Brahe’s discovery that stars changed over time; Kepler’s theories of planetary motion; the founder of modern science Galileo’s experiments and astronomical discoveries confirmed the heliocentric theory; Hubble’s discoveries about nebulae, other galaxies, the expanding universe, and the Big Bang Theory; Vera Rubin’s work on galaxy clustering, spiral galaxies, and dark matter; stellar astrophysicist Cecelia Payne’s study of high-luminosity stars, the Milky Way, and stellar evolution; astrophysicist Neil deGrasse Tyson‘s many books, writings, and TV appearances which have helped people understand the complex concepts of astrophysics.