Stars in our galaxy almost never collide because there is so much space between them. But the James Webb Space Telescope (JWST) has revealed that the early universe was much more chaotic.
A new study by astrophysicists at the University of California, Los Angeles (UCLA) found that ancient star systems were packed so tightly that stars often crashed into one another. Sometimes these collisions destroyed the stars, while other times they combined to form much larger stars.
This ongoing merging helps solve a big mystery about how black holes form. Slow, repeated collisions in these crowded clusters created huge stars with as much mass as many normal stars combined.
UCLA doctoral student Claire Williams said that when these giant stars died, they collapsed and formed intermediate-mass black holes. This process helps explain how supermassive black holes appeared so quickly after the Big Bang, which had puzzled astronomers before.
The team’s models also help explain the mysterious “little red dots” often seen by the JWST. They suggest these bright red spots are really dense star clusters in the middle of merging into huge stars and eventually black holes.
When a black hole forms at the center of a cluster, things change. Its strong gravity speeds up the nearby stars. Instead of merging, these fast-moving stars smash apart, creating huge clouds of gas that feed the black hole. Williams pointed out that this is similar to what happens at the center of the Milky Way, where a dense cluster of stars surrounds a central black hole.
UCLA astrophysicist Smadar Naoz said this idea brings together several different theories about how the early universe evolved. Back then, instead of neat spiral galaxies like we see today, there were tightly packed regions where stars formed. These ancient clusters were ideal places for intermediate-mass black holes to form and grow into the supermassive black holes we see in the universe now.