James Webb Space Telescope identifies the smallest free-floating brown dwarf

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The near-infrared camera (NIRCam) of the James Webb Space Telescope identifies the smallest free-floating brown dwarf with only three to four times the mass of Jupiter in the star cluster IC 348. NASA/ESA released its image on December 13, 2023.

The star cluster IC 348 is located about 1,000 light-years away in the famous Perseus star-forming region.

Brown dwarfs fall in the category between planets and stars in terms of mass. (Image credit: NASA/JPL-Caltech)

Brown dwarfs are more massive than gas giant planets (e.g., Jupiter) but less massive than the smallest stars. Generally, their mass is between 13 and 80 times the mass of Jupiter.

Brown dwarfs form through the gravitational collapse of giant molecular gas clouds (like stars), but their core gas pressure (hence temperature) is not high enough to ignite nuclear fusion (unlike stars) due to their insufficient mass. For this reason, brown dwarfs are called failed stars.

Three brown dwarf candidates in the star cluster IC 348 — View larger. Webb captures three brown dwarf candidates in the star cluster IC 348. (Image credit: NASA, ESA, CSA, STScI, and K. Luhman (Penn State University) and C. Alves de Oliveira (European Space Agency))

The research team has identified three brown dwarf candidates with the help of James Webb Space Telescope in the star cluster IC 348 with a mass three to eight times that of Jupiter.

According to the computer model, the smallest one has only three to four times the mass of Jupiter. The temperatures of these brown dwarfs are in the range of 830 to 1500 degrees Celsius.

Now the question arises that whether they are indeed brown dwarfs or free-floating rogue planets that were ejected from planetary systems.

The team can’t neglect the possibility of the latter, they argue that they are more likely to be brown dwarfs than ejected planets. For that they have given two reasons.

First, as the star cluster IC 348 is compact with low-mass stars, they are unlikely to be capable of producing massive planets.

Second, the star cluster IC 348 is young, only about five million years old. As a result, it is not possible to form giant planets and then eject them from their systems in such a short period of time.

A scientific paper has been published on the topic in The Astronomical Journal on December 13, 2023.

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