Astronomers Find Young Brown Dwarf with Circumstellar Disk

W1200-7845 was discovered through Disk Detective, a citizen science project funded by NASA and hosted by Zooniverse that provides images of objects in space for the public to classify, with the aim of picking out objects that are likely stars with disks that could potentially host planets.

Citizen scientists can look through ‘flipbooks’ —images of the same object in space, taken by NASA’s Wide-field Infrared Survey Explorer (WISE), which detects infrared emissions such as thermal radiation given off by the gas and dust debris in stellar disks.

A user could classify an object based on certain criteria such as whether the object appears oval (a shape that more resembles a galaxy) or round (a sign that the object is more likely a disk-hosting star).

“We have multiple citizen scientists look at each object and give their own independent opinion, and trust the wisdom of the crowd to decide what things are probably galaxies and what things are probably stars with disks around them,” said co-author Dr. Steven Silverberg, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research.

An artist’s impression of the brown dwarf W1200-7845 and its disk. Image credit: William Pendrill / NASA.

From there, professional astronomers follow up on crowd-classified disks, using more sophisticated methods and telescopes to determine if indeed they are disks, and what characteristics the disks may have.

In the case of W1200-7845, citizen scientists first classified the object as a disk in 2016. Dr. Silverberg and colleagues then looked more closely at the source with an infrared instrument on the Magellan 6.5-m telescopes at Las Campanas Observatory.

With these new observations, they determined that the source was indeed a disk around a brown dwarf within the ε Cha moving group, one of several young moving groups spread across the southern sky.

W1200-7845 is also very close to the Earth, at about 333 light-years away, making it the closest, young brown dwarf detected yet. “When it’s this close, we consider it to be within the solar neighborhood”, said co-author Maria Schutte, a graduate student at the University of Oklahoma.

“That proximity is really important, because brown dwarfs are lower in mass and inherently less bright than other objects like stars. So the closer these objects are to us, the more detail we’ll be able to see”.

The scientists now plan to zoom further in on W1200-7845 with other telescopes, such as the Atacama Large Millimeter Array (ALMA). They hope to see the brown dwarf’s disk itself, to measure its mass and radius.

“A disk’s mass just tells you how much stuff is in the disk, which would tell us if planet formation happens around these systems, and what sorts of planets you’d be able to produce”, Dr. Silverberg said.

“You could also use that data to determine what kinds of gas are in the system which would tell you about the disk’s composition”.

The researchers reported the discovery at the 236th Meeting of the American Astronomical Society (AAS).

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