NASA's SPHEREx Finds Water, Methane and CO2 in 37 Brown Dwarfs
SPHEREx spectra of 37 nearby brown dwarfs reveal water, methane, carbon monoxide and carbon dioxide, a new lab for giant-planet atmospheres.
NASA’s SPHEREx space telescope has measured the atmospheres of 37 nearby brown dwarfs and found water, carbon dioxide, carbon monoxide and methane in them. The study, led by Zafar Rustamkulov of Caltech/IPAC, appears in The Astrophysical Journal, and NASA described the results on October 8, 2026. Brown dwarfs are objects too heavy to be planets but too light to shine by fusing hydrogen the way stars do.
SPHEREx launched in March 2025 and takes about 3,600 images a day to map the entire sky. It measures brightness in 102 colors, which builds a spectrum for every source at infrared wavelengths that water vapor in Earth’s atmosphere largely blocks from the ground. The sample covers the full brown dwarf temperature range, from about 2,200 °C down to about minus 20 °C.
Until now, only a few dozen brown dwarfs had been studied in this kind of detail from space. Because they sit between stars and giant planets, a large and uniform sample works as a laboratory for atmospheres like Jupiter’s, and for the gas giants found around other stars (see our exoplanets guide). The molecules detected so far are the expected ones; the value is in having the same measurement for many objects at once. More on how these “failed stars” fit into stellar physics is in our guide to stars.
What to watch next: the team has thousands more brown dwarfs in the SPHEREx data still to analyze, which should show how their chemistry changes with temperature.
Primary source
This summary is based on NASA and the peer-reviewed paper. Read the original for full details, data and caveats.
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