pia20583-main_-wise_ldwarf
April 21, 2016

NASA discovers free-floating planet-sized object in the Milky Way

In 2011, astronomers reported our galaxy is likely filled with roaming planets not attached to a host star, and these worlds may in fact outnumber stars in the Milky Way.

Scientists have debated over whether these objects are true planets, or light stars known as brown dwarfs. Brown dwarfs form just like stars but don't have the mass to spark nuclear fusion at their cores.

In a new study published by The Astrophysical Journal, scientists identified one of these objects that may give answers to where these roaming objects came from.

Discovering objects throughout the galaxy

Scientists used information from NASA's Wide-field Infrared Survey Explorer (WISE) to identify the roaming, planetary-mass object inside a young star family, known as the TW Hydrae association. The newly found object, dubbed WISEA J114724.10-204021.3, or simply WISEA 1147, is believed to be between about 5 to 10 times the mass of Jupiter.

Since the object was discovered to be an affiliate the TW Hydrae group of very young stars, astronomers recognize that it is relatively young, around 10 million years old. Also, because planets need a minimum of 10 million years to develop, and even longer to get kicked out of a solar system, WISEA 1147 is probably a brown dwarf, the study team said.

"With continued monitoring, it may be possible to trace the history of WISEA 1147 to confirm whether or not it formed in isolation," study author Adam Schneider of the University of Toledo in Ohio, said in a NASA news release.

The study team said tracking the origins of free-floating objects and figuring out if they are planets or brown dwarfs is a struggle because they are so isolated.

"We are at the beginning of what will become a hot field – trying to determine the nature of the free-floating population and how many are planets versus brown dwarfs," said co-author Davy Kirkpatrick of NASA's Infrared Processing and Analysis Center (IPAC) at the CalTech.

One method to detect close roaming objects is movement in relation to other stars over time. The closer an object, the more it will seem to move against a background of more remote stars. By examining information from both sky surveys taken approximately 10 years apart, closer items jump out.

The brown dwarf WISEA 1147 was brilliantly red in survey pictures where the color red was assigned to longer infrared wavelengths, meaning that it's dusty and young.

"The features on this one screamed out, 'I'm a young brown dwarf,'" Schneider said.

After further evaluation, the astronomers discovered that this object is associated with the TW Hydrae group, which is around 150 light-years from Earth and just approximately 10 million years old. With an approximate mass between five and 10 times that of Jupiter, WISEA 1147 is one of the youngest and lightest brown dwarfs ever discovered.

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Image credit: NASA/JPL Caltech