Brown Dwarfs

Between Stars And Planets: Brown Dwarfs in IC 348

By Keith Cowing
Status Report
June 24, 2024
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Between Stars And Planets: Brown Dwarfs in IC 348
Brown Dwarfs in IC 348 (NIRCam Image) Larger image – NASA

Not quite stars, not quite planets — brown dwarfs are objects that fall in between. Within the star cluster shown in this image, Webb observed the tiniest, free-floating brown dwarf ever discovered.

Webb’s sharp infrared eye found this record-breaking brown dwarf in star cluster IC 348, which is about 1000 light-years away and only 5 million years old.

Studying brown dwarfs helps us understand star formation as well as exoplanets, or planets beyond our solar system. Not only is there overlap between the smallest brown dwarfs and the largest exoplanets, free-floating brown dwarfs come with no stars attached — unlike exoplanets, which can be hidden in the glare of their host stars.

But brown dwarfs aren’t the only free agents in space. Could this discovery be of an uncommon “rogue planet” instead? It’s unlikely: The surrounding stars are both young and low-mass, so they probably could not have produced and then ejected a giant planet in such a short time.

We still don’t quite understand how brown dwarfs this small are even able to form. Webb’s got more to do: Future surveys can search for similar objects to clarify their status, as well as the mysteries of their formation and composition.

This image: This image from the NIRCam (Near-Infrared Camera) instrument on NASA’s James Webb Space Telescope shows the central portion of the star cluster IC 348. Astronomers combed the cluster in search of tiny, free-floating brown dwarfs: objects too small to be stars but larger than most planets. They found three brown dwarfs that are less than eight times the mass of Jupiter, which are circled in the main image and shown in the detailed pullouts at right. The smallest weighs just three to four times Jupiter, challenging theories for star formation.

Image description: On the left is a large image of a star cluster and nebula, which takes up two-thirds of the view. Wispy filaments of pink-purple fill the middle of the image, curving left and right on either side of the center. The filaments on the right side form a dramatic loop that seems to extend toward the viewer. At lower left, additional filaments are colored yellowish. Two prominent, bright stars near the center show Webb’s eight-point diffraction spikes. Dozens of fainter stars are scattered across the image. In the bottom third, three small areas are circled and labeled 1, 2, and 3. On the right is a column of three smaller boxes labeled 1, 2, and 3, showing enlarged sections of the full image that align to the numbers in the larger image at left. A pair of faint stars are shown in box 1, while boxes 2 and 3 each highlight a single, faint star. The background in the top two images looks dusty, while the background in the third is dark gray.

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