15 Sep 2026

 

This starry view of the nearby star-forming region IC 348 is one of the largest images from the NASA/ESA/CSA James Webb Space Telescope released to the public so far. Using Webb, astronomers searched IC 348 for brown dwarfs, which are less massive than the smallest stars. The researchers discovered brown dwarfs just twice the mass of Jupiter, bringing the study of these curious objects into a new mass range.

 

The star-forming region IC 348 is located just 1000 light-years away in the constellation Perseus. In regions like IC 348, cold clouds of molecular hydrogen gas collapse to form new stars, creating glowing, sculpted scenes like this one. The star-formation process can create impressively varied objects, from massive stars that expire after only a few million years in core-collapse supernova explosions to the smallest and most common stars, which are long lived and produce powerful stellar storms.

The smallest stars weigh in at around 8% of the Sun’s mass. Below this mass lies a strange and intriguing class of objects called brown dwarfs. Brown dwarfs form in the same way that stars do, through the collapse of molecular clouds, but unlike stars, the cores of brown dwarfs never become hot enough to fuse hydrogen into helium (though many briefly fuse deuterium, or heavy hydrogen, early in their lives).

What’s still not clear – and what researchers hoped to learn by using Webb’s sensitive instruments to probe IC 348 – is how small are the smallest objects created by the star-formation progress. In other words, how small is the smallest brown dwarf?

Researchers seeking to answer this question first used Webb to study IC 348 in 2022, when they discovered brown dwarfs with masses as low as three to four times the mass of Jupiter. Now, the same research team has used Webb to probe even deeper into this region in search of even smaller brown dwarfs.

The team used Webb’s NIRCam (Near-Infrared Camera) in 2024 to capture the warm glow of young brown dwarfs and newborn stars that we see in this new image of IC 348. After selecting candidate brown dwarfs based on their colours and brightness, they followed up with Webb’s NIRSpec (Near-Infrared Spectrograph) in 2025 to conduct spectroscopic observations to study the masses of the brown dwarfs.

Researchers seeking to answer this question first used Webb to study IC 348 in 2022, when they discovered brown dwarfs with masses as low as three to four times the mass of Jupiter. Now, the same research team has used Webb to probe even deeper into this region in search of even smaller brown dwarfs.

The team used Webb’s NIRCam (Near-Infrared Camera) in 2024 to capture the warm glow of young brown dwarfs and newborn stars that we see in this new image of IC 348. After selecting candidate brown dwarfs based on their colours and brightness, they followed up with Webb’s NIRSpec (Near-Infrared Spectrograph) in 2025 to conduct spectroscopic observations to study the masses of the brown dwarfs.

These deep Webb observations revealed something remarkable: brown dwarfs with masses as low as just twice the mass of Jupiter – just 0.19% of the Sun’s mass. These are the least massive brown dwarfs known, and their existence poses a challenge to models of how stars form.

In addition to the discovery of these unexpectedly lightweight brown dwarfs, the Webb observations contained even more surprises. One of the lightest newfound brown dwarfs showed signs of a disc, suggesting that planets could be forming around it despite the brown dwarf being the mass of a planet itself.

While inspecting the spectra of IC 348’s brown dwarfs, the research team also found a feature that they attributed to hydrocarbons, which are molecules made only of hydrogen and carbon atoms. This feature has only been seen in the atmospheres of the lowest-mass brown dwarfs, suggesting that these extreme objects might exist in a spectral class of their own.

The stars and brown dwarfs of IC 348 aren’t the only attractions in this photo. A brilliantly detailed collection of protostars occupies the upper-right corner of the image. Several of these protostars are accompanied by Herbig-Haro objects, which are luminous regions that form when jets from growing newborn stars crash into the gas and dust around the star.

The long, narrow object that is oriented horizontally in this corner is HH 797, which was featured previously as a Webb Picture of the Month. Upon close inspection, this source is revealed to be two protostars with nearly parallel outflows. Just to the right of HH 797 is the propeller-shaped source HH 211, which features both narrow jets and broader outflows, and was also showcased in a previous image release.

 

[Image]

(A) Star-forming region IC 348 (NIRCam image)

(B) Collage of cutouts of star-forming region IC 348