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Free-Roaming Exoplanets May Be Born Away from Any Star

Dense gas clouds may lead to the formation of gas giants without any star around

Aug 19, 2013 17:21 GMT  ·  By
Gas clouds like these are small and dense enough to form planets
   Gas clouds like these are small and dense enough to form planets

Several hundred exoplanets have been found, but the vast majority of those were around other stars. That's to be expected since that's where we're looking for planets most of the time. But some free-floating planets have also been discovered, planets which roam the galaxy but aren't in orbit around any star.

Now, astronomers have found proof that these planets can form on their own, outside the influence of stars. Previously, it was believed that most of these free planets were ejected from their star systems.

But a team of astronomers has studied small dark clouds of gas in our galaxy, which turned out to be dense enough to support planetary formation.

These pockets of gas have been ejected from the Rosette Nebula, some 4,600 light years away from Earth.

Using several telescopes, astronomers were able to determine that these gas globulettes are incredibly small, on a galactic scale, some less than 50 times the distance from the Sun and Neptune in diameter.

The gas clouds also weigh no more than 13 Jupiters and travel away from their nebula at some 80,000 km/h.

"We found that the globulettes are very dense and compact, and many of them have very dense cores. That tells us that many of them will collapse under their own weight and form free-floating planets. The most massive of them can form so-called brown dwarfs," Carina Persson, an astronomer at Chalmers University of Technology and a member of the team that made the discoveries, explained.

Brown dwarfs are also called failed stars, as they are stars that weren't able to gain enough mass to start a nuclear fusion process in their cores. As such, they have more in common with gas giants than with stars, even though their formation process is very similar to those of actual stars.

While the globulettes observed now are just gas and dust clouds, they could eventually collapse into gas giants. Considering that there are many small gas clouds like these in our Galaxy, it's safe to assume that there are also many free-roaming planets that have formed this way.