Astronomers have discovered a planet from another galaxy which has ended up in the Milky Way, because of galactic cannibalism.
The extragalactic exoplanet and its host star, a red giant near the end of its life, are providing scientists with a sobering glimpse of the Earth's own fate.
They were discovered by astronomers using the European Southern Observatory's La Silla telescope in Chile.
Reporting in the journal Science, Dr Rainer Klement describes the planet, named HIP-13044b, as being about 1.25 times more massive than Jupiter.
It's orbiting a star about 2000 light-years from Earth in the direction of the southern constellation of Fornax (the Furnace).
They're part of the Helmi stream of stars, which originally belonged to a satellite dwarf galaxy devoured by our galaxy in an act of galactic cannibalism, between 6 and 9 billion years ago.
Klement says it's the first time, astronomers have detected a planetary system of extragalactic origin.
"Because of the great distances involved, there are no confirmed detections of planets in other galaxies. But this cosmic merger has brought an extragalactic planet within our reach."
Astronomers made the discovery thanks to tiny telltale wobbles in the star caused by the gravitational tug of the planet's orbit.
The planet's elliptical orbit brings it to less than one stellar diameter from the star's surface and its year takes just 16.2 Earth days.
Scientists hypothesise the planet's orbit was initially much larger, but contracted inwards during the star's red giant phase.
Clues about our own fate
The planet's unusual because it orbits a star nearing the end of its life.
It's also one of the few exoplanets known to have survived its host star's expansion into a red giant.
The star has since contracted and is burning helium. But it will expand again in the next stage of its evolution, meaning the planet may be doomed after all.
Dr Fred Watson from the Australian Astronomical Observatory says the study raises a range of issues.
"It demonstrates our own fate when the Sun approaches the end of its life in about 5 billion years time," says Watson.
"It poses questions about how large planets form, because the host star contains few elements heavier than hydrogen and helium, making it the only star of this type, known to have planets.
"That could mean the planet was captured by the star, or there are things about planetary formation which we don't yet understand.
Watson says because the planetary system is part of a galaxy that formed at about the same time as the Milky Way, and has since been consumed by our galaxy, it's provides another insight into our solar system's future.
"That's because our galaxy will collide with Andromeda in 3 to 5 billion years time."