A new theory shows that a single star could collapse into two black holes, providing an explanation for how super-massive black holes existed in the early universe.
Black holes are mysterious and scary things. They form when particularly massive stars collapse under their own weight, compressing further and further until all of their mass is condensed into a single point with infinite density. Black holes are more than just massive, world-eating monsters though; they are the mortar that holds galaxies together. At the center of the Milky Way sits a single super-massive black hole, whose gravitational force is strong enough to hold the galaxy together.
Super-massive black holes are created when smaller black holes eat surrounding matter and merge with other black holes, a process called accretion. Accretion takes a long time, and that has caused some confusion for scientists when studying the early universe. Super-massive black holes existed even before the universe had existed long enough for them to form. New research from Caltech however, might have an explanation.
The new research, headed by Christian Reisswig, NASA Einstein Postdoctoral Fellow in Astrophysics, relates the creation of these super-massive black holes to another large object: the super-massive star. Super massive stars are immense and short lived, existing only for a few million years. They remain in a stable state during this time because their photon radiation pushes back against gravity in what is called hydrostatic equilibrium.
You can thank a super-massive black hole for our galaxy looking the way it does.
The photon emission cools the star and that makes it becomes more compact, eventually leading to gravitational instability and collapse. Many models for the collapse of such stars predict that as the star’s mass collapses, the matter turns into a disk due to it’s rotational speed. However, Reisswig reasons that tiny perturbations in the star might lead to a non-symmetrical collapse and that would make the star’s mass clump at two points, instead of one. At sufficient temperatures, this could even accelerate the collapse and lead to two black holes being formed; one at each clump. These holes could then orbit each other before eventually merging into a single, larger black hole.
The research is purely theoretical, having been tested in computer models only, but it could explain how super-massive black holes existed in the early universe. “This is a new finding,” Reisswig says. “Nobody has ever predicted that a single collapsing star could produce a pair of black holes that then merge.