A circumbinary planet is a type of planet that orbits two stars instead of one. Because of the short orbits of some binary stars, the only way for planets to form is by forming outside the orbit of the two stars. However, new studies have shown that there is a strong hint that the planet and stars originate from a single disk.
Observations and discoveries[]
An artist impression of the giant planet PSR B1620-26 b, which is orbiting the binary system PSR B1620-26, a system which contains both a pulsar and a white dwarf star.
PSR B1620-26 b[]
The first confirmed circumbinary extrasolar planet was found orbiting the binary system PSR B1620-26, which contains a millisecond pulsar and a white dwarf. The system is located in the globular cluster M4. The existence of a third body was first reported in 1993, and was suggested to be a planet based on 5 years of observational data. In 2003 the planet was characterized as being 2.5 times the mass of Jupiter in a low eccentricity orbit, with a semimajor axis of 23 AU.
HD 202206 b[]
The first circumbinary extrasolar planet around a main sequence star was found in 2005 in the system HD 202206: a Jupiter-size planet orbiting a system composed of a Sun-like star and a brown dwarf.