Extragalactic planet

Artist's impression of HIP 13044 b, the first discovered planet of extragalactic origin. This planet was detected using the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory.

An extragalactic planet is a planet that is outside the Milky Way Galaxy. Other terms used to describe these are extragalactic extrasolar planet and exgaplanet.

Twin Quasar related planet

A microlensing event in the Twin Quasar gravitational lensing system was observed in 1996, by R. E. Schild, in the "A" lobe of the lensed quasar. It is predicted that a 3-Earth mass planet in the lensing galaxy, YGKOW G1, caused the event. This was the first extragalactic planet announced. This however is not a repeatable observation, as it is a one time chance alignment. This predicted planet lies 4 billion light years away.

Andromeda Galaxy planets

A team of scientists has used gravitational microlensing to come up with a tentative detection of an extragalactic exoplanet in Andromeda, our nearest large galactic neighbour. The lensing pattern fits a star with a smaller companion weighing just 6 or 7 times the mass of Jupiter. This suspected planet is the first announced in the Andromeda Galaxy.

HIP 13044

HIP 13044 is a star about 2000 light years away within the Milky Way galaxy which was found to have an exoplanet. However, the star is part of the Helmi stream of stars, a leftover remnant of a small galaxy that collided with and was absorbed by the Milky Way over 6 billion years ago. The star is over 6 billion years old, so although the star and its planet are now part of the Milky Way, they originally formed in another galaxy which either orbited the Milky Way or had a close pass to it. Thus the planet, HIP 13044 b, around HIP 13044 was once an extragalactic planet. The planet had almost certainly been engulfed by the star when it was in its red giant phase earlier, spending a few hundred thousand years inside the star.

See also

• Solar System planets
• Exoplanet
• Planet