Brown dwarfs grow lonelier with age, Hubble reveals

Many brown dwarfs - interstellar objects larger than Jupiter but smaller than the lowest-mass stars - have binary companions but they grow lonelier as they age, according to a recent study by the Hubble Space Telescope.

Brown dwarfs are too large to be a planet but are too small to be a star because they cannot sustain nuclear fusion, since they are less massive than even the smallest stars.

The team sampled some of the coldest and lowest-mass old brown dwarfs previously identified by NASA's Wide-Field Infrared Survey Explorer in the solar neighborhood but didn't find any binary pairs, suggesting that a binary pair of dwarfs is so weakly linked by gravity that they drift apart over a few hundred million years due to the pull of bypassing stars.

"Our Hubble survey offers direct evidence that these binaries that we observe when they're young are unlikely to survive to old ages, they're likely going to get disrupted. When they're young, they're part of a molecular cloud, and then as they age the cloud disperses. As that happens, things start moving around and stars pass by each other. Because brown dwarfs are so light, the gravitational hold tying wide binary pairs is very weak, and bypassing stars can easily tear these binaries apart," said lead author Clémence Fontanive of the Trottier Institute for Research on Exoplanets, Université de Montréal, Canada.

 All by myself... 🎶Hubble observations show that brown dwarfs – cosmic objects that are too small to be a star, but bigger than Jupiter – don't have long relationships with an orbiting companion.Pairs drift apart due to the pull of bypassing stars: https://t.co/lQ4iv8YY0g pic.twitter.com/ALQPIN3xro

— Hubble (@NASAHubble) March 21, 2024