Webb's Little Red Dots may hide primordial black holes

Why QSO1

QSO1 lies about 13.1 billion light-years away and is seen as it was just 700 million years after the Big Bang. It is almost entirely made of hydrogen and helium, the universe's first elements, which makes it potentially more pristine than other Little Red Dots.

Primordial black holes were first proposed by Stephen Hawking in the 1970s, but no hard evidence has emerged. A key problem is telling them apart from astrophysical black holes formed when massive stars collapse. "Little Red Dots could surround astrophysical black holes, and most probably many of them do, but they could also be primordial black holes, if primordial black holes exist," said Valerio De Luca.

What the models show

The researchers modeled how a Little Red Dot like QSO1 could arise from a primordial black hole, while respecting cosmological limits on how many such black holes can exist overall and within a given cluster. Of three scenarios considered, the most likely was a smaller primordial black hole that fed on surrounding gas and energy until it reached QSO1's size.

"The door was open on this theory," said Loris Del Grosso. "We've now cracked it open a little farther by showing some scenarios are more likely than others."

The team plans to examine the roughly 100 other Little Red Dots seen by JWST to estimate how many might have begun as primordial black holes. If they do exist, De Luca said, something must have created them in the early universe, which "would be a groundbreaking discovery in physics."