An article published in “The Astrophysical Journal” reports the identification of 64 brown dwarf candidates in the star cluster NGC 602 in the Small Magellanic Cloud, one of the Milky Way’s satellite galaxies. A team of researchers used the James Webb Space Telescope to obtain the sensitivity and resolution needed to detect possible objects halfway between the planet and the star about 200,000 light-years away. Follow-up studies are needed to verify these candidates, the first brown dwarfs to be verified outside the Milky Way. NGC 602 is poor in elements heavier than hydrogen and helium, a condition that was normal when the universe was young, further reason for interest in studying the processes within the cluster.

So far, brown dwarfs were only identified within the Milky Way, and about 3,000 of these objects are known. Their emissions are very weak in visible light and are concentrated in the infrared. This is another area of ​​astronomical research where highly-sensitive infrared instruments are invaluable, and the James Webb Space Telescope has already proved that it has the sensitivity and resolution needed to make new discoveries.

The authors of this study used the James Webb Space Telescope to examine NGC 602, a star cluster in the Small Magellanic Cloud that is young from an astronomical point of view. Astronomers are interested in studying star formation processes under conditions that are different from those in the Milky Way and more similar to those that were normal when the universe was young. In addition to stars, brown dwarfs are also of interest, and 64 candidates were found within NGC 602 with estimated masses between 5% and 8% of the Sun’s, meaning that they are between 50 and 84 times Jupiter’s mass.

The analysis of the locations of protostars and brown dwarf candidates indicates that they formed together, at the same time. Estimating the age of stars and protostars is much easier than estimating the age of brown dwarfs, so in this case, the researchers assumed that the brown dwarfs are between 2 and 3 million years old as well.

Peter Zeidler of AURA (Association of Universities for Research in Astronomy) / STScI (Space Telescope Science Institute), lead author of this study, explained that the results he and his colleagues obtained confirm that the mass distribution below the hydrogen fusion limit is simply a continuation of the stellar distribution. It appears that brown dwarfs form like stars and that they simply don’t grow to the point of having enough mass to become stars.

The authors of this study intend to continue their work on the brown dwarfs in the NGC 602 cluster. The next steps will be to confirm the candidates and the fact that they form in a similar way to stars. The first evidence for a brown dwarf came in 1994, and in the last thirty years, significant progress has been made in our knowledge of these objects, which are often considered failed stars. The possibility of studying brown dwarfs in another galaxy offered by the James Webb Space Telescope may bring further progress in our knowledge of the processes of star formation and substellar formation.