The duo was found with help from citizen science project Backyard Worlds
A pair of brown dwarfs with the widest separation ever seen has been found with the help of citizen scientists. The objects are 19 billion kilometres apart – around three times the distance between the Sun and Pluto.
Brown dwarfs are stellar objects that don’t have quite enough mass to sustain nuclear fusion, but are hot enough to radiate infrared energy. Pairs that are gravitationally locked are relatively rare. “Because of their small size, brown dwarf binary systems are usually very close together,” said Emma Softich, an astrophysics student at Arizona State University (ASU) who led the study. “Finding such a widely separated pair is very exciting.”
“Wide, low-mass systems like [this] are usually disrupted early on in their lifetimes, so the fact that this one has survived until now is pretty remarkable,” says co-author Dr Adam Schneider from George Mason University. The brighter of the pair was initially identified in an image taken by the Wide-field Infrared Survey Explorer (WISE) by members of the public taking part in the Backyard Worlds: Planet 9 citizen science project, who searched through WISE data for low-mass stars, as well as brown dwarfs.
Softich then searched through 3,000 Backyard World brown dwarfs, comparing the WISE images to other surveys looking for companions, eventually finding this pair in data from the Dark Energy Survey. Follow-up observations with the Keck Observatory revealed that the dwarfs were 130 lightyears from Earth, with a separation 129 times the distance between Earth and the Sun.
“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,” says Professor Adam Burgasser from the University of California San Diego, who helped with the study.
The team hopes that studying the brown dwarfs will give astronomers the ability to develop tools and procedures to help discover more binary brown dwarfs in the future.
“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 Professor Jennifer Patience, Softich’s adviser at ASU. bit.ly/ZooniverseBYWorldsP9