NASA’s SPHEREx finds brown dwarfs with water and methane, they drift in darkness without a host star and heated entirely from within

Brown dwarfs are unusual celestial objects that drift through space without orbiting a host star. Heated by their internal energy, these dim worlds have chemically complex atmospheres containing water and other molecules, according to a new study published in The Astrophysical Journal.

Scientists examined the atmospheres of these mysterious objects using NASA’s SPHEREx space telescope. As per the findings, as brown dwarfs cool and age, their atmospheric chemistry changes. Some pass through a transition in which their clouds thin out, allowing methane-rich atmospheric conditions to emerge. “No two brown dwarfs are alike. Even at the same temperature, their spectra look quite distinct,” said Zafar Rustamkulov, lead author of the new study.

What are brown dwarfs?

First identified in the 1990s, brown dwarfs form from collapsing clouds of gas, much like stars. However, they do not have enough mass to sustain hydrogen fusion in their cores, the process that powers stars. These objects share characteristics with both stars and planets. They emit heat and light but can also resemble giant planets such as Jupiter and Saturn.


Unlike most planets, free-floating brown dwarfs do not depend on a host star. They travel through space independently and gradually cool as they age. “They’re kind of goth,” said Zafar Rustamkulov, lead author of the study and a scientist at IPAC, Caltech’s science and data centre in Pasadena, California.

“Unlike exoplanets, free-floating brown dwarfs are completely independent celestial objects that will fade into eternity alone. We’re still learning how complex they are,” he added.

How NASA’s SPHEREx telescope studied brown dwarfs

NASA launched its SPHEREx infrared space telescope in March 2025. Its two-year mission is designed to map the entire sky and investigate the origins of the universe, while also studying stars, galaxies and the chemical ingredients associated with the formation of planetary systems.

For the new study, researchers analysed observations of 37 nearby brown dwarfs spanning a wide range of temperatures, from about 4,000 degrees Fahrenheit (2,200 degrees Celsius) to minus 10 degrees Fahrenheit (minus 20 degrees Celsius).

SPHEREx measures the brightness of objects across 102 different colours, covering visible red light and infrared wavelengths. These measurements produce spectra that allow scientists to identify the chemical signatures of different molecules. The observations revealed evidence of water, carbon dioxide, carbon monoxide and methane in brown dwarf atmospheres.

“We’re seeing the signatures of these molecules and how they change from object to object across the entire temperature regime,” said study co-author J. Davy Kirkpatrick, a scientist at Caltech’s IPAC. The researchers are analysing additional observations to investigate the range of atmospheric conditions found across these objects.

Could brown dwarfs support alien life?

The discovery of water and other molecules in brown dwarf atmospheres does not mean that these objects support life. A 2013 report by Space.com, citing researchers, cited challenges such as cooling temperatures and potentially harsh radiation. Another study by researchers from the University of Edinburgh claimed that alien life could live in the upper layers of a brown dwarf’s atmosphere, which have temperatures and pressures similar to Earth’s. “You don’t necessarily need to have a terrestrial planet with a surface,” the study’s leader Jack Yates, a planetary scientist at the University of Edinburgh, told Science magazine.