Which cosmic object was the first discovered of its kind beyond the Solar System?

51 Pegasi b is the landmark exoplanet that opened the modern era of planetary discovery. Michel Mayor and Didier Queloz announced it in 1995 after detecting the star’s wobble caused by the planet’s gravity. The planet is a hot Jupiter, orbiting its star in only a few days and much closer than Mercury is to the Sun. This discovery earned them the 2019 Nobel Prize in Physics and transformed the search for other worlds.