Scientists Spot Foreign Planet Straying Into Milky Way

(Nov. 19) -- Astronomers have discovered an alien planet in our midst.

The newly found planet is believed to have come from outside the Milky Way galaxy -- the remnant of another, fading galaxy that was consumed by our own. It's stuck on a 16-day orbit around a fading red giant star about 2,000 light-years from Earth.

The planet, dubbed HIP-13044b, is believed to be about 1.25 times larger than Jupiter, in our own solar system. It was spotted by a sophisticated, 4-meter mirrored telescope operated by astronomers at the European Southern Observatory in Chile.

AFP / Getty Images

An artist's impression shows HIP-1304b, an exo-planet detected inside the Milky Way but believed to have come from outside our galaxy.

It's the first planet ever detected inside the Milky Way that's believed to be foreign-born. About 500 other planets have already been discovered that are believed to originate from outside our solar system but inside our galaxy.

But perhaps what fascinates scientists most about their new find is what it reveals about so-called "intergalactic cannibalism" -- evidence that between 6 billion and 9 billion years ago, the Milky Way gobbled up another smaller galaxy, in which this planet's sun once lived.

"This discovery is very exciting," Rainer Klement of the Max Planck Institute for Astronomy in Heidelberg, Germany, told the BBC. "For the first time, astronomers have detected a planetary system in a stellar stream of extragalactic origin. This cosmic merger has brought an extragalactic planet within our reach."

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The new planet is also unusual in that it's one of the only known bodies to have survived -- so far -- the death throes of the star it orbits. The star first expanded into a red giant and then contracted, burning helium. That pattern could give scientists ominous clues about what could happen to the Earth when our sun begins to die.

"It demonstrates our own fate when the sun approaches the end of its life in about 5 billion years time," Fred Watson, of the Australian Astronomical Observatory, told that country's ABC News.

Klement and his team have published their findings in this week's issue of the journal Science.