The glowing green nebula in this JWST image surrounds the star cluster IC 348, which is the subject of a recent study by Kevin Luhman (Penn State University) and Catarina Alves de Oliveira (European Space Agency). Using JWST’s Near-Infrared Camera, Luhman and Alves de Oliveira searched the cluster’s young stellar population for free-floating brown dwarfs — objects that are less massive than stars but more massive than most planets — and discovered multiple candidates with masses down to just twice the mass of Jupiter. Follow-up JWST spectroscopy confirmed the masses of these objects, making them the lowest-mass brown dwarfs known to date. In addition to their mass, these newly discovered brown dwarfs are remarkable because their spectra show evidence of hydrocarbon molecules, the exact identities of which are not yet known. Luhman and Alves de Oliveira proposed that low-mass brown dwarfs bearing this chemical signature be inducted into a new spectral class called “H” for “hydrocarbon.” To add to the intrigue of these objects, the authors also discovered signs of circumstellar disks around two of them, suggesting that they may be capable of forming and harboring planets. To learn more about the low-mass brown dwarfs in IC 348, be sure to check out the full research article linked below.
Citation
“A New Spectral Class of Brown Dwarfs at the Bottom of the IMF in IC 348,” K. L. Luhman and C. Alves de Oliveira 2025 ApJL 986 L14. doi:10.3847/2041-8213/addc55