Nearby Brown Dwarfs May Harbor Planet: Failed Star System Nearest to the Sun

Astronomers have taken a closer look at the closest pair of failed stars to the Sun and now, they've discovered that this dynamic duo may harbor a planet. The findings reveal a little bit more about this unusual system and reveals that planets can exist even under difficult circumstances.

Failed stars are known as brown dwarfs. They usually have a mass below eight percent of the mass of the Sun, which means they're not massive enough to burn hydrogen in their centers. This recently-studied system is known as Luhman 16AB, and is located just 6.6 light-years away.

In order to better study this system, the researchers used the FORS2 instrument on ESO's Very Large Telescope to examine the brown dwarfs once every five or six days over two months. This allowed them to detect tiny displacements of the two objects in their orbit.

"The two brown dwarfs are separated by about three times the distance between the Earth and the Sun," said Yuri Beletsky, one of the researchers, in a news release. "Binary brown dwarf systems are gravitationally bound and orbit about each other. Because these two dwarfs have so little mass, they take about 20 years to complete one orbit."

In fact, both objects have a mass between 30 and 50 Jupiter masses. By comparison, the Sun has a mass of about 1,000 Jupiter masses. This low mass in particular is what drastically impacts the orbits in the system. By closely examining the brown dwarfs, the researchers spotted some very small deviations from the expected motion of the dwarfs around each other. This seemed to be a strong indication that a companion perturbs the motion of one of the two brown dwarfs. In other words, it's likely a planetary-mass object is causing the deviation.

"Further observations are required to confirm the existence of a planet," said Henri Boffin, one of the researchers, in a news release. "But it may well turn out that the closest brown dwarf binary system to the Sun turns out to be a triple system!"

The findings are published in the journal Astronomy & Astrophysics.