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 is a star about 2000 light years away within the Milky Way galaxy which was announced 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. Further investigation revealed that the planet does not exist and that the detection was due to poor data sampling and incorrect correction for the Earth's orbital motion.
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- Discover Magazine; Bad Astronomy Blog, "Exoplanet found… from another galaxy!!", 18 November 2010
- Jones, M. I.; Jenkins, J. S. (2014). "No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044". Astronomy & Astrophysics 562: id.A129. arXiv:1401.0517. Bibcode:2014A&A...562A.129J. doi:10.1051/0004-6361/201322132.