Too big to be a planet but too small to be a star, brown dwarfs bridge the gap between giant planets and tiny stars. Formed from the collapse of gas and dust, brown dwarfs range in size between 13 and 80 times the mass of Jupiter but never become large enough to sustain nuclear fusion in their cores, like a star does (hence their nickname of “failed stars”). Yet, after their formation, some brown dwarfs retain a star-like disk of swirling gas and dust, collisions in which could potentially generate planets.
One such brown dwarf disk system, W1200-7845, has recently been identified by researchers from MIT and the University of Oklahoma, aided by the work of citizen scientists. What makes this discovery particularly exciting is that it is the closest brown dwarf to Earth with a disk younger than 5 million years old. This means that the dim light from W1200-7845 will be easier for astronomers to probe for more detail on these cosmic oddballs.
“We discovered the youngest brown dwarf disk within 102 parsecs (332 light-years) of the Sun, putting W1200-7845 in the solar neighborhood,” Maria Schutte, a graduate student involved in the discovery at the University of Oklahoma, said in a statement. “There are not many examples of young brown dwarfs so close to the Sun, so W1200-7845 is an exciting discovery.”
W1200-7845 was first brought to the attention of astronomers in 2016 when citizen scientists scanning through images of space as part of NASA’s Disk Detective project classified the object as a disk. With a target in mind, Schutte and the team directed the infrared instrument on the Magellan 6.5-meter telescopes at Las Campanas Observatory in Chile to study the system. The resulting observations told the team that the brown dwarf was located 332 light-years away in a cluster of stars that travel across the sky together (called a moving group).
“W1200-7845 is in a moving group that is about 4 million years old, which puts it at an ideal age to be a benchmark object in terms of investigating the formation and early evolution of brown dwarfs,” Schutte said.
The team, who announced their findings at the virtual meeting of the American Astronomical Society, hope to use telescopes such as the Atacama Large Millimeter Array (ALMA) in Chile to delve deeper into the brown dwarf’s disk and assess its potential to produce planets.
“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,” Steven Silverberg, study co-author and postdoc in MIT’s Kavli Institute for Astrophysics and Space Research, explained. “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.”
Like the researchers, the work of citizen scientists is not over either. A revamped version of Disk Detective has just been launched, boasting current images with better special resolution. In particular, the team are hoping for more detections of “Peter Pan” disks – disks that should be old enough to have formed planets but have not.