Lonely Worlds

While exoplanets have been all the rage of late, most of the distant worlds discovered so far have been located in solar systems like ours, where the planets revolve around a star.

Now, for the first time, astronomers have spotted a new breed of planets, floating alone in the dark of space far from the light of any star.

The discovery is based on a joint Japan-New Zealand survey that scanned the center of the Milky Way galaxy during 2006 and 2007, revealing evidence for up to 10 free-floating planets roughly the mass of Jupiter.

The isolated orbs, also known as orphan planets, are difficult to spot, and had gone undetected until then. The team thinks these lone worlds, located at an average approximate distance of 10,000 to 20,000 light-years from Earth, were probably ejected from developing planetary systems.

“Although free-floating planets have been predicted, they finally have been detected, holding major implications for planetary formation and evolution models,” says Mario Perez, exoplanet program scientist at NASA Headquarters in Washington.

The finding also indicates that there are many more free-floating planets that can’t be seen: indeed the team estimates there are about twice as many of them as stars!

If that proves to be the case, these worlds would be at least as common as planets that orbit stars – adding up to hundreds of billions of lone planets in our Milky Way galaxy alone.

“Our survey is like a population census,” explains David Bennett, co-author of the study. “We sampled a portion of the galaxy, and based on these data, can estimate overall numbers in the galaxy.”

The study appears in the latest issue of the journal Nature. Image credit: NASA/JPL-Caltech

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