Volunteers Help NASA Double the Known Population of Brown Dwarfs

Approximately 200,000 citizen scientists helped NASA locate brown dwarfs.

A group of NASA volunteers has helped astronomers find more than 3,000 possible brown dwarfs, strange cosmic objects that are too small to be stars but too large to be planets. The discoveries came through Backyard Worlds: Planet 9, a NASA citizen science project that lets people search real space telescope data from home.

Brown dwarfs are often called “failed stars.” Like stars, they form from clouds of gas and dust. But they do not have enough mass to keep nuclear fusion going in their cores. That means they never shine like true stars. Instead, they glow faintly, mostly in infrared light, which makes them hard to find. NASA describes them as gas balls about the size of Jupiter but less massive than stars.

The new study, led by astronomer Adam C. Schneider of the U.S. Naval Observatory, reports 3,006 new motion-confirmed L and T dwarf candidates. Of those, 2,357 are likely L-type dwarfs and 649 are likely T-type dwarfs. L and T dwarfs are different classes of cool, dim objects. T dwarfs are usually colder than L dwarfs, and both can help scientists better understand the space between planets and stars.

The work may more than double the number of known L and T dwarfs, once the candidates are confirmed. The study also identifies 28 objects that appear to move through space with larger stars, meaning they may be companions to those stars. Nine more objects may be binary systems made of two ultracool dwarfs.

Citizen Scientists to the Rescue

The discoveries came from a public effort that has lasted nearly 10 years. According to NASA, about 200,000 volunteers have helped with Backyard Worlds: Planet 9. The new paper has 75 authors, and 61 of them are non-working scientists.

“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.

The project used data from NASA’s Wide-field Infrared Survey Explorer (WISE) and its later mission, NEOWISE-R, which ended in 2024. These telescopes scanned the sky in infrared light, which is useful for finding cool objects that do not shine brightly in visible light. Volunteers searched through images, looking for objects that moved across the sky over time. That motion is one clue that an object may be close enough to belong to our cosmic neighborhood.

The method is simple in idea but hard in practice. Volunteers compare images taken at different times, looking for tiny dots that shift position. NASA says some volunteers went even further, building their own search tools and data-analysis software.

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For each candidate, the researchers provide measurements of motion, brightness in different wavelengths, estimated spectral types and distance estimates when possible. That information helps scientists decide which objects should be studied next with more powerful telescopes.

Spectroscopic observations are still needed to confirm the objects’ spectral types and learn more about them. Spectroscopy breaks light into its parts, much like a prism makes a rainbow. From that light, astronomers can learn about an object’s temperature, chemistry and other traits.

Brown dwarfs can help scientists learn how stars form, how planetary systems develop and how many low-mass objects exist in the Milky Way. NASA says the new list has already helped researchers find unusual objects, including extreme T subdwarfs and other rare ultracool objects.

For the volunteers, the work is also deeply personal.

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“Dreams do come true,” said Mayahuel Torres Guerrero, a Backyard Worlds volunteer from Mexico City, after learning she would be listed as a co-author.

The discovery shows that space science is no longer limited to people with access to major observatories. Anyone with a computer can help sort through the enormous amount of data modern telescopes collect. In this case, thousands of small discoveries added up to one of the largest brown dwarf catalogs ever produced.

Backyard Worlds: Planet 9 is still active. NASA says the project continues to search through more than two billion sources observed by WISE and NEOWISE-R. That means more brown dwarfs, nearby stars or other dim objects may still be waiting in the data.