November 14, 2012
Orphaned Planet May Help Explain Planet And Star Formation
[ Watch the Video: Artists Impression of Free-Floating Planet ]
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers have identified a body that is most likely a planet wandering throughout space without a parent star.
The free-floating planet candidate is the closet such object to the Solar System observed so far, lying at a distance of about 100 light-years away.
The object gives astronomers a view of the exoplanets that future instruments aim to image around stars other than the Sun.
Free-floating planets are planetary-mass objects that roam around space, without any ties to a star. Possible examples of these planetary bodies have been shown before, but without knowing their ages, it was not possible for astronomers to know whether they were really planets or brown dwarfs.
Astronomers have now found that CFBDSIR2149 seems to be part of a nearby stream of young stars known as the AB Doradus Moving Group. The team found the object in observations from CFHT and harnessed the power of the VLT to examine its properties.
The AB Doradus Moving Group is the closet group to the Solar System. Its stars drift through space together and are thought to have formed at the same time. If the object is associated with this moving group, it is possible to find out more about it, including its temperature, mass, and what its atmosphere is made of.
The link between CFBDSIR2149 and the moving group is a vital clue that allows astronomers to find the age of the newly discovered object. This is the first isolated planetary mass object ever identified in a moving group.
"Looking for planets around their stars is akin to studying a firefly sitting one centimeter away from a distant, powerful car headlight," said Philippe Delorme, lead author of the new study. "This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up."
Free-floating objects like the one observed are thought to form either as normal planets that have been booted out of their home systems, or as lone objects like the smallest stars or brown dwarfs.
"These objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process," Delorme said. "If this little object is a planet that has been ejected from its native system, it conjures up the striking image of orphaned worlds, drifting in the emptiness of space."
If the planet is not associated with the AB Doradus Moving Group, it is trickier to be sure of its nature and properties, and may instead be characterized as a small brown dwarf. Both scenarios represent important questions about how planets and stars form and behave.
"Further work should confirm CFBDSIR2149 as a free-floating planet," Delorme concluded. "This object could be used as a benchmark for understanding the physics of any similar exoplanets that are discovered by future special high-contrast imaging systems, including the SPHERE instrument that will be installed on the VLT."
A paper about the findings was published in the Astronomy & Astrophysics journal.