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Pair of brown dwarfs orbit each other 12 billion miles apart

It’s not uncommon for stars to be found in binary pairs, where two stars are gravitationally bound together and orbit each other. Sometimes, you even find triple star systems with three stars bound together. But typically, stars in these configurations are relatively close together. Now, though, astronomers have spotted a pair of brown dwarfs, which are objects in between planets and stars, which have the widest separation found to date.

The brown dwarf pair, called CWISE J014611.20-050850.0AB, are a mind-bending 12 billion miles apart — that’s more than three times the distance between Pluto and the sun. They are especially notable because brown dwarf pairs generally have less gravitational force binding them than a pair of full-blown stars would have. “Because of their small size, brown dwarf binary systems are usually very close together,” said lead author Emma Softich of Arizona State University in a statement. “Finding such a widely separated pair is very exciting.”

An artist’s rendition of a binary system of brown dwarfs like CWISE J014611.20-050850.0AB.
An artist’s rendition of a binary system of brown dwarfs like CWISE J014611.20-050850.0AB. William Pendrill

The pair were discovered with the W. M. Keck Observatory on Maunakea, Hawaiʻi, using its Near-Infrared Echellette Spectrometer, or NIRES instrument. “Keck’s exceptional sensitivity in the infrared with this instrument was critical for our measurements,” said co-author Adam Burgasser. “The secondary brown dwarf of this system is exceptionally faint, but with Keck we were able to obtain good enough spectral data to classify both sources and identify them as members of a rare class of blue L dwarfs.”

Citizen scientists played a role in helping this discovery come about as well. As part of NASA’s Backyard Worlds project, members of the public were invited to search astronomical data to look for indications of brown dwarfs. The researchers in this study looked through the Backyard World’s identified brown dwarfs and searched for companions to them.

When the researchers found indications of a binary pair, they used NIRES to confirm the pair, located around 130 light-years away.

“Binary systems are used to calibrate many relations in astronomy, and this newly discovered pair of brown dwarfs will present an important test of brown dwarf formation and evolution models,” said co-author Jennifer Patience.

The research is published in The Astrophysical Journal Letters.

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