PASADENA, Oct. 14 -- The best computer models of brown dwarf atmospheres, the failed stars that sit between planets and stars, still struggle to reproduce what NASA's SPHEREx telescope sees as these objects cool through their cloudiest phase, a gap that matters because astronomers lean on those models to read worlds they cannot visit.

SPHEREx, an infrared telescope launched in March 2025 and managed by NASA's Jet Propulsion Laboratory, is mapping the entire sky and takes about 3,600 images a day. Brown dwarfs are a side project. A team led by Zafar Rustamkulov of IPAC at Caltech analyzed 37 nearby ones spanning roughly 2,200 to minus 20 degrees Celsius, measuring their light in 102 colors, NASA said. The results appeared in The Astrophys...