NASA’s SPHEREx space telescope is shedding light on brown dwarfs, celestial objects that blur the line between stars and exoplanets.
First discovered in the 1990s, brown dwarfs form from collapsing clouds of gas, like stars do, but they aren’t enough to sustain hydrogen fusion in their cores. In contrast to most planets, however, brown dwarfs drift in darkness, ungoverned by a host star and heated from within.
“They’re kind of goth,” said Zafar Rustamkulov, lead author of the new study and a scientist at IPAC, Caltech’s science and data center in Pasadena, California.
Only a few dozen of these “dark wanderers” have been studied in detail with space-based telescopes.
Enter NASA’s SPHEREx, an infrared space telescope launched in March 2025 and managed by the agency’s Jet Propulsion Laboratory in Southern California.
The study authors analyzed SPHEREx observations of 37 nearby brown dwarfs spanning the full brown dwarf temperature range, from about 4,000 to minus 10 degrees Fahrenheit.
Spotting brown dwarfs is something of a side project for SPHEREx.
For years, brown dwarfs have been spotted by other observatories, including NASA’s James Webb Space Telescope and retired Spitzer Space Telescope.
Some of the brown dwarfs observed by SPHEREx are in a dynamic stage of life when their exotic clouds thin out, giving way to methane-rich atmospheres.
The science analysis of the SPHEREx data is being conducted by a team of scientists at 13 institutions across the United States and in South Korea and Taiwan, led by Jamie Bock, principal investigator and by JPL’s Olivier Doré, the project scientist.