Astronomers Discover Giant Alien Planet That Shouldn't Be There

Astronomers have discovered a planet that really shouldn't be where it was found. They've spotted a giant planet orbiting its star at 650 times the average Earth-Sun distance. The new discovery throws a wrench in planet formation theories, revealing that these strange systems can exist outside our own galaxy.

The planet itself weighs in at 11 times Jupiter's mass. Known as HD 106906 b, the planet is unlike anything the astronomers have seen before. Planets that are located close to their stars, like Earth, are thought to coalesce from small asteroid-like bodies born in the primordial disk of dust and gas that surrounds a forming star. However, this process acts far too slowly to grow giant planets that are far from their stars. Another theory states that large planets can form from a fast, direct collapse of disk material. However, these primordial disks rarely contain enough mass in their outer reaches to form a planet like HD 106906 b. That said, there are a few theories.

"A binary star system can be formed when two adjacent clumps of gas collapse more or less independently to form stars, and these stars are close enough to each other to exert a mutual gravitation attraction and bind them together in an orbit," said Vanessa Bailey, one of the researchers, in a news release. "It is possible that in the case of HD 106906 system the star and planet collapsed independently from clumps of gas, but for some reason the planet's progenitor clump was starved for material and never grew large enough to ignite and become a star."

Yet there are problems with the scenario. The mass ratio of the two stars in a binary system is typically no more than 10-to-1. In the case of the new planet, though the mass ratio is more than 100-to-1. That would be extremely unusual if not impossible under current planet formation theories.

"Every new directly detected planet pushes our understanding of how and where planets can form," said Tiffany Meshkat, one of the researchers, in a news release. "This planet discovery is particularly exciting because it is in orbit so far from its parent star. This leads to many intriguing questions about its formation history and composition. Discoveries like HD 106906 b provide us with a deeper understanding of the diversity of other planetary systems."

The findings are published in The Astrophysical Journal Letters.