This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In our solar system's corner of the galaxy, stars rarely collide. It makes sense: Space is vast, and stars have room to roam.
Even in most of the present-day universe, stellar collisions are rare. The James Webb Space Telescope, however, peers deep enough into space to see the universe as it was not too long after the Big Bang. Its observations have revealed extraordinarily compact stellar systems, raising the possibility that collisions between stars were once much more common.
A new study—led by UCLA astrophysicists and currently published on the arXiv preprint server—finds that in the early universe, stellar systems were extremely dense, with stars frequently hitting each other. These collisions could happen at either very rapid speeds, which destroyed the stars, or more slowly, in which case they merged into one. Repeated mergers could produce a single extraordinarily massive star, which might eventually collapse into a black hole.
Some of these gigantic stars eventually became black holes. The finding could help explain how the seeds of supermassive black holes formed early enough to grow into the enormous black holes already present in the young universe. "Perhaps the strangest outcome of our simulations is that stars can merge repeatedly within the cluster until they form one gigantic star with a mass equal to that of an entire cluster," said UCLA doctoral student and corresponding author Claire Williams.
"When a star this huge reaches the end of its life, models suggest that it may have no option but to collapse into itself and form a massive black hole." The center of the Milky Way provides a nearby example of the same basic ingredients: a massive black hole embedded within a dense nuclear star cluster. The model suggests that once a black hole is present, its gravity accelerates nearby stars, causing collisions close to the black hole to destroy them rather than merge them and release gas into the surrounding region. "One place in the nearby universe where collisions between stars are common is the galactic center," Williams said.
"In our model, once these very massive stars turn into intermediate-mass black holes, the system resembles our own galactic center, which is a black hole surrounded by a dense star cluster." The origin of supermassive black holes has been a mystery. Astronomers expected they would grow gradually, but the James Webb Space Telescope has found them forming quickly after the Big Bang. The new research is not the first to propose stellar collisions as the mechanism, but the modeling ties together observations, such as intriguing "little red dots" (LRDs), and theoretical models to identify clear pathways to collisions for stars within dense clusters and the formation of supermassive black holes.
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