Webb finds brown dwarfs only twice Jupiter’s mass
IC 348
A nearby region where new stars are forming.
brown dwarf
An object made like a star but too cool to shine like a normal star.
NIRSpec
A Webb instrument that studies patterns in an object’s light.
What happened
On Sept. 15, 2026, NASA, the U.S. space agency, released a new image from the James Webb Space Telescope, or Webb. Webb is an infrared space telescope built through an international partnership. The image shows IC 348, a star-forming region about 1,000 light-years away in Perseus. It is one of Webb’s largest public images so far. NASA’s release ESA’s overview
The image also contains a scientific surprise. Astronomers found brown dwarfs with masses as low as about twice Jupiter’s mass. These are among the least massive brown dwarfs known.
The background
Brown dwarfs sit below the lightest stars in mass. They can weigh only a few times as much as Jupiter. They form when clouds of molecular hydrogen collapse under their own gravity, like clouds that make stars. However, their centers never become hot enough to turn ordinary hydrogen into helium for long. They therefore do not shine like normal stars.
The smallest stars weigh about 8 percent as much as the Sun. That makes the new objects important. They approach the lower edge of objects made by the star-forming process.
The research team had already found brown dwarfs about three to four times Jupiter’s mass in Webb observations from 2022. For the new study, the team used Webb’s NIRCam in 2024. It captured the warm glow of young stars and brown dwarfs. The team then used NIRSpec in 2025. This instrument studied their light patterns. The measurements pointed to objects with about twice Jupiter’s mass, or about 0.19 percent of the Sun’s mass.
Why it matters
The key question is not only how heavy these objects are. It is how they were born. If planet-mass objects can form from collapsing clouds, star formation may continue to much smaller masses than models predicted.
One of the lightest brown dwarfs also shows signs of a disk. A disk is a flat collection of gas and dust around an object. Small planets might grow inside it. That possibility is striking because the central object itself has only about a planet’s mass. The observation does not prove that planets are forming there. It gives scientists a new test for their models.
What Webb also saw
The panorama shows protostars, or stars still gathering material. Some send narrow jets into nearby gas and dust. The impacts create glowing regions called Herbig-Haro objects. The image includes the detailed structures HH 797 and HH 211.
The spectra also showed a feature linked to an unidentified hydrocarbon. Hydrocarbons contain only hydrogen and carbon. This feature has appeared in the atmospheres of the lowest-mass brown dwarfs. It may point to a special class of very small objects.
What remains unknown
Scientists still do not know whether the smallest objects formed like stars. They could instead be rogue planets thrown out of other planetary systems. The possible disk does not yet show that a planet exists. Researchers also need to identify the unusual hydrocarbon feature. They want to know how often these planet-mass objects appear in other star-forming regions.
What comes next
General Observer Program 4866 will compare planet-mass objects across star-forming regions. Future, longer observations may find even fainter and smaller objects. Those results could show whether IC 348 is unusual or typical. They could also reveal how the boundary between stars and planets really works.
Webb finds tiny objects near the star–planet boundary
📰 Full story: Webb finds brown dwarfs only twice Jupiter’s mass
A space telescope found brown dwarfs about twice Jupiter’s mass.
brown dwarf
An object that forms like a star but never becomes hot enough to shine normally.
spectrograph
A tool that spreads light into patterns for scientists to study.
Herbig-Haro object
A bright spot made when a young star’s jet hits nearby gas and dust.
💡 The gist
- Webb photographed IC 348, a place where stars are forming.
- It found brown dwarfs about twice Jupiter’s mass.
- The result tests how stars and planets can begin.
What did Webb see?
NASA, the U.S. space agency, uses the James Webb Space Telescope, a telescope in space. On Sept. 15, NASA released a huge view of IC 348. IC 348 lies about 1,000 light-years away, in Perseus. It is one of Webb’s largest public images. NASA’s report
The picture shows gas, dust, young stars, and jets. Jets are narrow streams of material. They shoot from newborn stars. They crash into nearby gas and dust. The glowing spots are called Herbig-Haro objects.
What is a brown dwarf?
A brown dwarf forms when a cloud of gas collapses. A true star becomes hot enough to fuse ordinary hydrogen. A brown dwarf does not get that hot. It cannot shine like a normal star.
Scientists first found brown dwarfs about three to four times Jupiter’s mass. That happened during Webb observations in 2022. The new study found objects about twice Jupiter’s mass.
Scientists used Webb’s NIRCam in 2024. It captured the warm glow of young objects. They then used NIRSpec in 2025. NIRSpec is a spectrograph. It spreads light into patterns. Those patterns help scientists study an object’s nature.
Why does this matter?
Brown dwarfs form like stars. This suggests that star-like formation may create very small bodies. One brown dwarf seems to have a disk around it. A disk is a flat ring of gas and dust. Small planets might grow there. Scientists have not confirmed a planet there.
The biggest mystery is the object’s origin. It may have formed from a collapsing cloud. Or it may be a planet thrown from another system.
What comes next?
Researchers will compare IC 348 with other star-forming regions. They will study how common these tiny objects are. Longer observations may find even smaller bodies. Scientists will also investigate the unusual hydrocarbon feature in their light.
Webb finds a tiny almost-star
📰 Full story: Webb finds brown dwarfs only twice Jupiter’s mass
A space telescope found a small object that is not quite a star.
IC 348
A place where stars are born.
brown dwarf
A small body that cannot become a bright star.
What happened?
NASA, the U.S. space agency, uses the James Webb Space Telescope, a telescope in space. It looked at IC 348, a place where stars are born. It found a brown dwarf, a body that cannot become a bright star.
One was about twice as heavy as Jupiter. Jupiter is a large planet.
Stars begin inside clouds of gas. The gas is pulled together. The middle grows hot. A real star gets hot enough to shine. This little body stays too cool. So it is not a true star.
Webb also saw baby stars sending thin streams. The streams hit gas and dust. Then bright spots appear.
One brown dwarf has a ring of gas and dust. Small planets might grow there. Scientists do not know yet.
They will watch IC 348 again. They will search other star-making places, too. They want to learn how tiny star-like bodies begin.