Planets Exist Around
Other Stars
Year of Discovery: 1995
What Is It? Planets—even planets like Earth—exist around other stars.
Who Discovered It? Michel Mayor and Didier Queloz
Why Is This One of the 100 Greatest?
One of the great questions for humanity has always been: Are we alone? Science has
long asked: Are we the only solar system with planets—and the only one with planets that
could support life? The discovery of planets around other stars makes it likely that other
planets exist capable of supporting life.
Of great importance to astronomers, the discovery of other solar systems lets them test
their theories on the origin of planets and solar systems. The discovery of distant planets has
fundamentally changed how we perceive our place in the universe.
How Was It Discovered?
In the sixth century B.C., Greek scientist Anaximander was the first to theorize that
other planets must exist. In 1600 Italian priest and astronomer Giordano Bruno was burned
at the stake by the Catholic Church for professing the same belief. American astronomers
were actively searching through giant telescopes for planets orbiting other stars by late the
1940s.
Michel Mayor was born in 1942 and even as a child was fascinated by stars and astronomy. With his collaborator, Antoine Duquennoy, he joined the many astronomers searching for small objects in the universe. But Mayor searched not for planets, but for brown
dwarfs—cool, dim objects thought to form like stars, but which failed to grow massive
enough to support hydrogen fusion and thus never lit up with starry furnace and fire. Too
big for planets, too small to become stars, brown dwarfs were a galactic oddity.
Astronomers, however, had a problem: telescopes can’t see planets and brown dwarfs
because they don’t give off light. Instead, astronomers searched for slight side-to-side wobbles in the motion of a star caused by the gravitational tug of a large planet (or brown
dwarf).
Some tried to detect such wobble by carefully measuring the position of a star over the
course of months or years. Others (Mayor included) looked for this wobble by using Dopp-
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