A new paper in The Astrophysical Journal details the discovery of almost 100 cool worlds known as brown dwarfs, which were found with the help of a huge group of citizen scientists. 

Brown dwarfs are sometimes referred to as “failed stars” because they are between the most massive planets and the smallest stars in mass. They don’t have enough mass to sustain nuclear reactions. As a result, they are cold and dim, which also makes them very difficult to find. In fact, we only have success finding them in the relatively close vicinity of our Sun. The Backyard Worlds project found nearly 1,500 new brown dwarfs, and these hundred included in the paper are the coolest of the bunch, with temperatures approaching Earth’s. 

The data for this project was collected from a variety of programs run by the National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory (NSF’s NOIRLab) and then made available to some 100,000 volunteers through the Backyard Worlds project. Those volunteers carefully scoured the images for moving pixels and identified changes in the images, and several observatories, including NASA’s Spitzer Space Telescope, did follow-up observations to gather the temperature estimates.

The discovery of these very cool planets helps bridge a gap in the low-temperature range of brown dwarfs. According to lead author Aaron Meisner: These cool worlds offer the opportunity for new insights into the formation and atmospheres of planets beyond the Solar System. This collection of cool brown dwarfs also allows us to accurately estimate the number of free-floating worlds roaming interstellar space near the Sun.

Co-author Jackie Faherty explained: This paper is evidence that the solar neighborhood is still uncharted territory and citizen scientists are excellent astronomical cartographers. Mapping the coldest brown dwarfs down to the lowest masses gives us key insights into the low-mass star formation process while providing a target list for detailed studies of the atmospheres of Jupiter analogs.

My favorite part of this story is that it keeps referencing the nearness of the objects to our own Sun when in fact, the closest one is 23 light-years away and most are 30-60 light-years away. The neighborhood, indeed.

More Information

Keck Observatory press release 

NOIRLab press release 

“Spitzer Follow-up of Extremely Cold Brown Dwarfs Discovered by the Backyard Worlds: Planet 9 Citizen Science Project,” 2020 August 20, Astrophysical Journal