Historically, when did people realize that the Sun is a star?
As this wonderful website explains, the first person to come up with the idea that stars and the Sun are the same thing, just at different distances, was Anaxagoras, in about 450 B.C. Later, Aristarchus, around 220 B.C., thought similarly. In 1600 A.D., Giordano Bruno was burnt at the stake for heresy, for asserting that the Sun is a star, among other things. It wasn't until the mid-1800s, after the work of Galileo, Kepler, Huygens, Newton, and finally, Friedrich Bessel, that it could be proven. The distance to other stars was calculated, and it was found that stars were about as bright as the Sun, when you account for the difference in distance. Also, chemical composition and surface temperature could be determined, and this added further evidence.
This page was last updated June 28, 2015.