NASA’s SPHEREx Reads the Chemistry of 37 Brown Dwarfs

Some objects in space are too big to be planets and too small to be stars. They glow faintly, they never ignite, and they are hard to study. NASA’s newest sky-mapping telescope just read the chemistry of 37 of them, almost as a side job.

What brown dwarfs are

Brown dwarfs, NASA says, are “celestial objects that blur the line between stars and exoplanets.” They form from collapsing clouds of gas, just like stars, but they never gain enough mass to sustain hydrogen fusion in their cores. That is why people often call them failed stars. Astronomers first discovered them in the 1990s.

“They’re kind of goth,” said Zafar Rustamkulov, a scientist at IPAC, Caltech’s science and data center in Pasadena, and lead author of the new study.

102 colors per object

SPHEREx is an infrared space telescope that launched in March 2025, and NASA’s Jet Propulsion Laboratory manages it. Its main job is mapping the whole sky, taking about 3,600 images a day. From orbit, it sees wavelengths that Earth’s atmosphere blocks from ground-based telescopes.

For each of 37 nearby brown dwarfs, SPHEREx measured brightness in 102 colors and built a spectrum, a chemical fingerprint of the atmosphere. The results, published in The Astrophysical Journal, show water, methane, carbon monoxide and carbon dioxide. The sample spans the full brown dwarf temperature range, from about 4,000 down to minus 10 degrees Fahrenheit (2,200 to minus 20 degrees Celsius).

Models that can’t keep up

The data also exposed gaps in theory. According to Rustamkulov, “the models are struggling to match the data.” And these 37 are only the start. SPHEREx is imaging thousands more brown dwarfs for the first time in the deep red and infrared, and the team is still analyzing them.

“The findings are a call to action to explore even more of these dark worlds,” said coauthor J. Davy Kirkpatrick, also of IPAC.

Sources

• NASA: NASA’s SPHEREx Telescope Sees Menagerie of Brown Dwarfs (8 October 2026)
• Rustamkulov et al., The Astrophysical Journal (2026)