or extrasolar planets
Planets that orbit stars other than the Sun.
The existence of extrasolar planets, many light-years from Earth, was confirmed in the early 1990s with the detection of three bodies circling a pulsar . The first planet revolving around a more sunlike star, 51 Pegasi, was reported in 1995. Within a decade over 100 stars with one or more planets were known. Current detection methods, based on the planets' gravitational effects on the stars they orbit, have revealed only planets much more massive than Earth; some are several times the size of Jupiter . A number of them have highly elliptical orbits, and many are closer to their stars than Mercury is to the Sun. These findings have raised questions regarding astronomers' ideas of how Earth's solar system formed and how typical it is.