51 Pegasi b , also called Bellerephon or 51 Peg b , is the first extrasolar planet that was discovered orbiting a main-sequence star . It is 50 light years away from our solar system in the constellation Pegasus . 51 Pegasi b , also unofficially named Bellerophon and abbreviated as 51 Peg b , is an extrasolar planet approximately 50 light-years away in the constellation of Pegasus .