The discovery of 51 Pegasi b led to new methods for finding exoplanets

Scientists have found thousands of exoplanets since the discovery of the first planet outside our solar system.
By Lliane Hunter | Apr 17, 2018
In 1995, astronomers discovered 51 Pegasi b, the first planet orbiting a sun-like star 50 light years from earth. The discovery heralded the beginning of the hunt for exoplanets, writes Marina Koren for The Atlantic.

51 Pegasi b is an unusual planet, says Michael Mayor one of the astrophysicists to discover it. The planet is about half the mass of Jupiter and orbits extremely close to its starone trip only taking four days. "It was absolutely not expected from theory," Mayor says, describing the initial discovery. His co-founder, astrophysicist Didier Queloz, confirms the shock of their discovery. "51 Peg completely changed our perspective of how we could look for planets," he says.

The makeup and trajectory of Pegasi b generated new possibilities for research, so astrophysicists implemented a technique for detection called the transit method. Following this method, astronomers focus telescopes on a star, and watch for any dimming in its brightness. Dimming occurs when a planet passes in front of its star and blocks out the light, explains Koren.

Since 51 Pegasi b's discovery, scientists have used the transit method to identify 3,717exoplanets, with more than 900 expected to have a rocky surface like Earth's. NASA plans to launch TESS (Transiting Exoplanet Survey Satellite) on Wednesday in order to survey over 200,000 stars for two years. Astronomers predict TESS will find more than 1,600 new exoplanets, with 70 expected to be Earth-sized.


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