Blimey! This is cool. The planet that revolves around a dwarf galaxy known as HIP 13044b has reportedly merged with our galaxy between six and nine billion years ago.
It is estimated that the planet is at least 200 light years from our Earth.
Because of the vast distance, astronomers at the European Southern Observatory (ESO) in La Silla, Chile, could not detect the planet visibly, using the 2.2 metre-diameter telescope.
Instead, they inferred its existence from tiny telltale wobbles of the star.
These are caused by the gravitational tug of its large orbiting companion, which the astronomers detected with a high-resolution spectrograph attached to the telescope.
Rainer Klemen, of the Max-Planck Institute for Astronomy in Heidelberg, Germany, said: ‘This discovery is very exciting. For the first time, astronomers have detected a planetary system in a stellar stream of extragalactic origin.’
The planet is orbiting a star which is approaching the end of its life, having exhausted its hydrogen fuel and gone through a stage of massive expansion – called the red giant phase – in which it probably consumed the inner planets in its solar system.
It has now contracted again and is burning helium in its core.