Failed stars: James Webb photographs newborn brown dwarfs in the Orion Nebula

Using the James Webb Telescope (JWST), astronomers have managed to get images of the smallest and coldest protoplanetary disks in the Orion Nebula. Now they’re giving birth to brown dwarfs.

Infrared image of the Orion Nebula. The inset shows protoplanetary disks around brown dwarfs photographed by James Webb. Source: NASA/ESA/CSA, Mark McCaughrean/ESA, Massimo Robberto/STScI/JHU, Kevin Luhman/Penn State, Catarina Alves de Oliveira/ESA.

Back in the late 1990s, the Hubble telescope captured the Orion Nebula, one of the closest regions of active star formation to Earth. During the observations, it was able to detect many gas-dust disks around newborn stars (also called proplyds). This data has greatly enriched researchers’ knowledge of how exoplanets form, and was one of the main findings of Hubble’s entire lifetime. 

Researchers have long suspected that some of the coldest and smallest proplyds detected by Hubble are actually surrounded by brown dwarfs rather than stars. This is the name given to objects occupying an intermediate position between gas giants and brown dwarfs. There may be some thermonuclear reactions in the interior of brown dwarfs, but they are rather fleeting, and their power never compares to their own luminosity. This is why brown dwarfs don’t “light up” but shrink and dim.

Until recently, astronomers were unable to confirm the nature of some of the more suspicious proplyds detected by Hubble. Everything changed when the JWST was commissioned. Its capacity proved to be sufficient to carry out the test.

JWST observations have confirmed that about 20 objects in the Orion Nebula are cool enough to be brown dwarfs. The smallest of them can have masses as low as five Jupiter masses. Two more objects are near the mass limit for sustained thermonuclear reactions. In their case, it is still unclear whether they are very small stars or very large brown dwarfs.

Astronomers said the JWST data helped them better understand the formation of brown dwarfs, their relationship to stars and planets, and the possible existence of their own planets. And it’s just the beginning. The Orion Nebula contains at least a few hundred more faint objects that may be brown dwarfs and could be targets for future JWST observations.

We previously reported on how James Webb helped astronomers find the first population of brown dwarfs outside the Milky Way.

Provided by Phys.org