Planet 9 volunteers double known population of brown dwarfs

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A new paper from NASA's Backyard Worlds: Planet 9 project announces that volunteers have essentially doubled the number of known brown dwarfs, with over 3,000 new discoveries made over the past 10 years since the project began. Brown dwarfs are balls of gas the size of Jupiter, less massive than stars. There's one for every three or four stars near the sun.

Although brown dwarfs are common, they can be hard to spot because they shine so faintly compared to stars. Having twice as many brown dwarfs to study allows astronomers a deeper understanding of these elusive objects. Already, this vital new list of brown dwarfs has revealed a new variety of objects—the extreme T subdwarfs and many other rarities, such as ultra-cool objects and a brown dwarf that appears to have aurorae. It has also helped us inventory the distribution of mass in our galaxy and map our cosmic neighborhood.

The discoveries are published in a paper on the arXiv preprint server, led by astronomer Adam Schneider from the U.S. Naval Observatory. They represent work done over the course of ten years aided by a team of roughly 200,000 volunteers. Of the paper's 75 authors, 61 are volunteers. Two of the other authors began their work with the team as volunteers and then embarked on careers in astronomy.

"I truly appreciate the recognition for all of us who collaborated, in some way, on this effort," said Walter Ruben Robledo, an amateur astronomer and Backyard Worlds: Planet 9 volunteer from Cordoba, Argentina.

"When I received the news about the co-authorship, I thought: Yes, dreams do come true," said another volunteer, Mayahuel Torres Guerrero, from Mexico City.

The volunteers discovered these brown dwarfs in images taken by NASA's retired Wide-field Infrared Survey Explorer (WISE) and Near-Earth-Object WISE Reactivation mission (NEOWISE-R). They examined the data using the Zooniverse citizen science platform, searching for moving objects by blinking images taken over a 16-year time period. Some volunteers even contributed by building their own search tools and data analysis software.

Publication details

Adam C. Schneider et al, Three Thousand Motion-Confirmed L and T Dwarf Candidates from the Backyard Worlds:~Planet 9 Citizen Science Project, arXiv (2026). DOI: 10.48550/arxiv.2604.01323

Journal information: arXiv

Key concepts

GalaxiesBrown dwarfsSpace telescopes

Provided by NASA