Humanity's understanding of its place in the universe began changing in a big way 20 years ago this month.
On Oct. 6, 1995, Michel Mayor and Didier Queloz of Switzerland's Geneva Observatory announced the discovery of the huge, scorching-hot 51 Pegasi b, the first alien planet ever found around a sunlike star.
The first exoplanets of any type were spotted in 1992 by astronomers Aleksander Wolszczan and Dale Frail, who found two worlds circling a fast-rotating stellar corpse called a pulsar. As monumental as this discovery was, the 51 Peg b announcement perhaps resonated even more, since pulsars are a far cry from "normal" stars like Earth's sun. [The Strangest Alien Planets]
The new field of exoplanet science has progressed rapidly in the last two decades: Astronomers have now confirmed the existence of nearly 2,000 planets beyond our own solar system. (The exact number varies depending on which database is consulted.)
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