Simulations of the early universe suggest that stars may have collided frequently in densely packed clusters. Researchers say slower collisions could have caused repeated mergers, creating exceptionally massive stars that later collapsed into black holes larger than those formed from individual stars. These black holes could have served as seeds for the first supermassive black holes.
The proposal addresses a longstanding puzzle: the James Webb Space Telescope has detected supermassive black holes from when the universe was less than a billion years old. Growing to millions or billions of times the Sun’s mass through feeding and mergers would ordinarily take at least that long, prompting researchers to consider whether the black holes began from larger-than-usual seeds.
In the team’s simulations, dense clusters allowed stars to merge repeatedly. Some could grow to an extraordinary size before collapsing, potentially forming intermediate-mass black holes. Team member Claire Williams of the University of California, Los Angeles, said the model suggests a star could reach a mass comparable to that of an entire cluster before collapsing into a massive black hole.
The same process could also help explain the JWST’s Little RED Dots: compact objects seen in the early universe that appear to have vanished by the time the cosmos was about two billion years old. The researchers suggest these objects may have been dense star clusters undergoing repeated collisions, with the resulting massive stars eventually forming intermediate-mass black holes.
According to the proposed explanation, the conditions that enabled such clusters were more common when the universe was young and chaotic. As the cosmos expanded and cooled, these regions developed into more orderly galaxies, potentially removing the extreme environments needed to sustain Little Red Dots. The study was published in The Astrophysical Journal on October 26.
Sources: Space.com.