Sunday, September 25, 2011

Planets Without Stars, Wanders Galaxy Alone

Astronomers have found a new type of planet drifting by itself through space, unbounded to any star. By scanning the crowded center of our Milky Way Galaxy, the international team discovered up to 10 Jupiter sized "orphan planets; about 10,000 to 20,000 light-years from Earth. Details appeared in a May 19 study in Nature.

Such lonely planets had long been predicted, but this is the first time data support their existence. "Our survey is like a population census; says co-author David Bennett of the University of Notre Dame in South Bend, Indiana. We sampled a portion of the galaxy, and based on these data, can estimate overall numbers in the galaxy."

Can a planet orbits without star?

Because such planets are extremely hard to see, the finding implies a huge number await discovery, perhaps twice as many as there are stars in our galaxy. Further, the survey couldn't spot objects much smaller than Saturn, but theories suggest earth-like planets should be even more plentiful, leading to even more lonely solo worlds.

The team suspects the new found planets likely formed in a star system before the gravity from another planet or star hurled them into space. Left to their own devices, orphan planets would orbit the galactic center just like our Sun (and other stars) does. The discovery will affect how astronomers envision the birth of solar systems and planets, as well as how these objects interact over time.

"Results suggest that planetary systems often become unstable," says Bennett. "With planets being kicked out from their places of birth." - B. A.

A "Starless" planet: Astronomers have found a Jupiter-sized planet
by itself in open space, as shown in this artist's depiction; they now suspect such worlds
could be twice as common in our galaxy as stars. NASA/JPL-Caltech.

Source: Astronomy Magazine, September 2011.

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