New Delhi: Over the past ten years, citizen scientists working with NASA’s Backyard Worlds: Planet 9 project have discovered over 3,000 new brown dwarfs, doubling the number of such exotic objects known. Brown dwarfs are gas giants that straddle the mass gap between stars and planets, and are considered failed stars. There is about one brown dwarf for every three or four stars near the Sun. While brown dwarfs are common, they can be hard to spot because they do not shine brightly like stars. Having a large sample of brown dwarfs to study allows astronomers to improve their understanding of these elusive objects.

Already, the expanded catalogue of brown dwarfs has revealed a new variety of objects, including extreme T subdwarfs that are about 10 billion years old, about twice the age of the Sun, containing 75 times the mass of Jupiter, along with other rarities such as ultra-cool brown dwarfs with white dwarfs companions in binary systems, and a brown dwarf that appears to have aurorae. The research also helps scientists inventory the distribution of mass in the galaxy, and better map the neighbourhood that we live in. A team of about 200,000 volunteers helped with the project.

How the volunteers discovered the brown dwarfs

The brown dwarfs were discovered in observations captured by NASA’s retired Wide-field Infrared Survey Explorer (WISE) and NEar-Earth object WISE Reactivation mission (NEOWISE-R). The data was analysed using the Zooniverse citizen science platform, looking for moving objects by comparing images taken over a 16-year time period. Some volunteers built their own search tools and data analysis software. The volunteers continue to sift through two billion sources captured by the WISE and NEOWISE-R missions. The search cannot be automated, and it requires human eyes to spot these dim objects, as well as differentiate them from imaging artefacts. Readers interested in participating can do so here.