SPHEREx's all-sky survey compares the cloudy atmospheres of faint brown dwarfs
NASA's SPHEREx telescope, which scans the whole sky in infrared light, is recording faint brown dwarfs, and a peer-reviewed study in The Astrophysical Journal compares their atmospheres. The authors report that temperature, chemistry and clouds vary from one object to the next. Clouds can distort a spectrum and temperature estimates, and a similar atmosphere is no proof that a brown dwarf formed the way a planet did.
Science··Midday
A sky survey doubles as a brown-dwarf spectrum collection
NASA's SPHEREx space telescope observes many faint brown dwarfs while it maps the whole sky in infrared light. Because a broad survey picks out many candidates together, researchers can compare numerous examples at once instead of staying on a single target for a long observation.[1]
A peer-reviewed study in The Astrophysical Journal used SPHEREx measurements to compare the atmospheres of these objects. Spectra across infrared wavelengths show where molecules absorb light, and the study reports that temperature, chemistry and clouds change from one object to the next.[1]
Brown dwarfs sit between stars and giant planets
A brown dwarf begins like a star, as a collapsing cloud of gas, but falls short of the mass needed to keep hydrogen fusion going in its core. That leaves some of its traits close to those of giant gas planets. Free-floating ones need not circle any star and glow faintly from their own internal heat.[1]
Astronomers can set the molecules seen in these atmospheres beside those found in the solar system's giant planets. Cold, dim brown dwarfs are where observations have been thinnest, and the survey helps close that gap.[1]
Clouds can distort a spectrum and blur the temperature estimate
Interpreting these cloudy atmospheres is tricky, the authors caution: a cloud deck reshapes the spectrum that reaches the telescope and can skew temperature estimates. What the data pin down are particular atmospheric properties, not the inside of each object.[1]
Resemblance in an atmosphere is no proof that a brown dwarf took the same route to existence as a planet. SPHEREx data are processed into an archive that is available to researchers and the public.[1]
