Nature loves to break the neat little boxes we use to classify stuff. In astronomy, one of these box breakers is brown dwarfs. These objects have both stellar and planetary qualities, existing on the cusp of both. New research continues to blur the line and the latest observations are no different. Brown dwarfs in the Orion Nebula seem to possess a protoplanetary disk.
Brown dwarfs can be as light as 13 times the mass of Jupiter (probably even lighter). They form like stars but have clouds. They are simply not heavy enough to start nuclear fusion in their interior and for that reason, they will never shine like a star.
Still, their starlike formation might allow them to get a disk of material around them. Decades ago, Hubble was used to find these disks within the Orion Nebula. In particular, it focused on proplyds, the protoplanetary disks illuminated by the ultraviolet light of the brightest and most massive stars in the nebula. The quest now was to find more around the smallest stellar objects.
“Stars are born within massive clouds of gas and dust in space that can be light years across, which are called nebulae,” co-lead author Kevin Luhman, professor of astronomy at Penn State, said in a statement. “For decades, astronomers suspected that soon after a star coalesces within a nebula, planets are born within a disk of gas and dust surrounding the newborn star, known as a protoplanetary disk.”
“Some of the objects born in nebulae like Orion have masses that are too small for them to undergo hydrogen fusion, so they are cool and faint and do not qualify as full-fledged stars,” added co-lead author Catarina Alves de Oliveira, head of the Science Operations Development Division at the European Space Agency. “These star-like bodies that lack fusion are known as brown dwarfs. The question is, can we find proplyds around any of the brown dwarfs in Orion?”
The observations conducted by JWST highlighted 20 likely and two borderline brown dwarfs with suspected proplyds. The smallest of them was just five times the mass of Jupiter. Two of the candidates were already identified as proplyds by Hubble and the JWST observations suggest that they are the coolest and least massive known protoplanetary disks.
The observations provide important clues about the nature of brown dwarfs and how they relate to both stars and planets. However, more observations are necessary to fully fill in the gaps in our knowledge of these objects. In the Orion Nebula, JWST has discovered other peculiar substellar objects called JuMBOs.
A paper on this discovery is available on arXiv ahead of its publication in The Astrophysical Journal.
