Universe Today
Brown dwarfs are notoriously difficult to find. These “failed stars” aren’t big enough to sustain nuclear fusion, and therefore aren’t as bright as more traditional main sequence stars. In fact, they’re nearly invisible in optical light, and faintly visible in infrared. But thanks to dozens of citizen scientists combing through archival infrared datasets from the Wide-field Infrared Survey Explorer (WISE), and a paper published in the Astronomical Journal detailing their work, we now have an additional set of over 3,000 candidate new brown dwarfs in our stellar neighborhood, more than doubling the total number found so far.
The volunteers were part of Backyard Worlds: Planet 9, a Zooniverse project that has been running for around 10 years. Finding these particular worlds is a sweet spot for human pattern recognition - which makes it a great fit for crowd-source science projects. Picking brown dwarfs out of a static background of distant galaxies is difficult for automated search algorithms, which are very prone to false positives. Instead, human pattern finders processed “flipbooks” of time-resolved WISE images, tracking faint objects moving across the sky over periods of years.
Volunteers weren’t alone on this journey though - there were also professional scientists behind the effort, who vetted over 100,000 volunteer submissions, eventually confirming 3,006 objects with significant “proper motion” - which means that the objects moved relative to distant, static background stars over the years. That metric is useful both for confirming that the brown dwarf was near to our solar system, but also to estimate its age based on the group of moving stars it is likely traveling with.
Fraser talks about dark matter in brown dwarfs.The 3,006 objects can be broken down into two categories, out of the three that comprise the cataloging scheme for brown dwarfs. 2,357 objects are “L Dwarfs” - with dusty, complex atmospheres and clouds formed out of minerals. Whereas 649 objects are “T Dwarfs”, which are cold enough that atmospheric dust settles and methane becomes dominant in their atmosphere. An additional 80 objects had the spectral signature of either an L or T Dwarf, but they were either too faint or the volunteers couldn't pinpoint their position accurately enough to confirm their movement.
But they were able to confirm some other rare astronomical setups. 28 of the objects in the study were co-moving companions of larger, more visible stars. Even more tantalizingly, there were 9 candidate binary systems made up of two ultracool dwarfs. Wide ultracool binaries are incredibly rare, as they are easily disrupted by the pull of other passing stars over millions of years, so finding 9 of them in a single new data set will provide plenty of study time to help confirm or develop new orbital mechanics theories.
Many of the 61 volunteer authors of the paper (out of a total of more than 200,000 volunteers that contributed to the project over the years) were absolutely thrilled to get a scientific credit to their name. “When I received news about the co-authorship, I thought: Yes, dreams do come true,” said volunteer Mayahuel Torres Guerrero of Mexico City. But the mission isn’t done yet.
Jorge Sanchez, a PhD candidate at Arizona State, discusses how to find Brown Dwarfs in images. Credit - Origins Seminars YouTube ChannelBackyard Worlds: Planet 9 volunteers are still busy sifting through 2 billion other images captured by WISE and the Near-Earth-Object WISE Reactivation mission (NEOWISE-R). Odds are with that much data to sort through, they can use all the help they can get - and if you decide to contribute, you might just get a credit on a high-impact academic paper for your efforts!
Learn More:
NASA - NASA Volunteers Double Known Population of Brown Dwarfs
A.C. Schneider et al. - Three Thousand Motion-Confirmed L and T Dwarf Candidates from the Backyard Worlds:~Planet 9 Citizen Science Project
UT - These Rare Star Systems Are A New Tool To Understand Brown Dwarfs
