Early universe's 'little red dots' may be black hole stars

sciencehabit writes: It’s as if the baby universe had caught a case of measles. Since NASA’s JWST observatory began peering into the distant universe in 2022, it has discovered a rash of “little red dots”—hundreds of them, shining within the first billion years of the 13.8-billion-year-old universe, so small and red that they defied conventional explanation. Only in the past few months has a picture begun to emerge. The little red dots, astronomers say, may be an entirely new type of object: a colossal ball of bright, hot gas, larger than the Solar System, powered not by nuclear fusion, but by a black hole.

“I think we’re closing in on an answer,” says Jenny Greene, an astrophysicist at Princeton University. The objects, which some astronomers are calling “black hole stars,” could be a missing link in the evolution of galaxies and help explain the rapid growth of supermassive black holes that lie at their hearts. “The big breakthrough of the past 6 months is actually the realization that we can throw out all these other models we’ve been playing with before,” says astronomer Anna de Graaff of the Max Planck Institute for Astronomy.

Given how common little red dots appear to be in the early universe, theorists are beginning to wonder whether this giant-ball-of-gas phase is an essential part of black hole growth and the evolution of galaxies. “We’re probably looking at kind of a new phase of black hole growth that we didn’t know about before,” de Graaff says. Greene agrees: “I can totally imagine that the Milky Way was a little red dot that got its black hole started and then kind of piddled along for the rest of cosmic time.”

If the red dots do turn out to be black hole stars, it will be precisely the sort of breakthrough expected from JWST—and the kind of discovery astronomers live for. Unraveling the mystery of little red dots has “been the most fun I’ve ever had in my career,” Greene says.