Webb’s survey of IC 348 identified extremely low-mass brown dwarfs, including objects around twice Jupiter’s mass. Their existence challenges models of how a collapsing cloud can make something so small.
RESEARCH · OPEN QUESTION
A star nursery with unusually small residents
IC 348 is a young star-forming region roughly 1,000 light-years away in Perseus. Webb’s infrared sensitivity allowed astronomers to search through the crowded region for objects too cool and faint to shine like normal stars. Among them were brown dwarfs with estimated masses down to about twice the mass of Jupiter. [1] [2]
Brown dwarfs are often described as objects between stars and planets. They form as isolated objects rather than as planets orbiting a star, but they never become massive enough to sustain ordinary hydrogen fusion like a star.
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JOIN THE SIGNAL →Why two Jupiter masses is difficult
Star formation begins when parts of a cold molecular cloud collapse under gravity. At very low masses, theory has to explain how such a small clump can separate from its environment, collapse, and avoid gathering much more material. Finding brown dwarfs at only a few Jupiter masses pushes that process into a regime where the difference between star-like formation and planet-like mass becomes especially striking. [2]
The discovery does not mean Webb found “planets with no stars” in the ordinary sense. Mass alone does not tell you how an object formed. That distinction is one reason these bodies are scientifically useful.
The planet–brown-dwarf boundary is not a clean line
Categories in astronomy are partly based on physics and partly on formation history. A giant planet may have a mass similar to a low-mass brown dwarf while having a completely different origin. An isolated object can therefore look planet-like on a scale while belonging to a star-forming population.
For Dark Nova, this is a useful example of a real boundary problem: nature does not always organize itself around the labels people prefer. Webb is expanding the known population into the zone where those labels become hardest to apply.
What else Webb saw in IC 348
The large Webb panorama also shows young stars, dusty structure, and protostellar jets slamming into surrounding material. Those features let researchers study very different outcomes of the same broad star-forming environment—from stars to exceptionally low-mass brown dwarfs. [1]
That context matters. The tiny objects were not found in isolation from a formation site; they were found inside a region actively producing new stars and substellar bodies.
The next question
The important next step is determining how common these ultra-low-mass brown dwarfs are and whether current formation models can reproduce their numbers. Spectra can also refine temperatures, compositions, and masses.
If the population continues below the masses already detected, astronomers may have to rethink how efficiently star-forming clouds fragment into the smallest self-gravitating objects.
Sources and further reading
- NASA Science — Webb Reveals Dynamic Panorama of Star Formation (September 15, 2026)
- ESA/Webb — Star-forming region IC 348 (NIRCam image) (September 15, 2026)
Sources checked September 29, 2026. Written with AI assistance using the linked primary or agency sources. Reported findings are separated from Dark Nova editorial explanation. Send a correction or source.