Binary black holes, systems consisting of two black holes in close orbit around each other, synchronize their spins before they merge together, according to new research.
The moment creates a beautiful sight in simulations of how space works.
In stellar clusters - groups of stars that can contain as few as a dozen to as many as millions - binary black holes can collide with massive stars. This collision can cause an explosion, disrupting or even destroying the star.
Black holes are astronomical objects with a gravitational pull so strong that not even light can escape them. They form when the core of a massive star collapses in on itself.
While it was commonly believed that the binary black holes formed in star clusters always have had random spins, scientists say that stellar collisions cause them to align their spins.
“When a massive star is torn apart by a binary black hole, it creates two separate streams of debris, each spiraling around one of the black holes,” explained Northwestern University’s Fulya Kıroğlu.
Kıroğlu a graduate student, led the research that has been accepted for publication in The Astrophysical Journal Letters.
“Initially, the direction of these spinning debris clouds is random. However, as the black holes get closer, powerful tidal forces begin to realign these clouds, gradually influencing the spin direction of the black holes themselves,” she explained.
Over time, Kıroğlu said that the process leads to black hole mergers with a “slight but consistent alignment of their spins.”
That’s something that had been seen in invisible ripples emanating from merging binary black holes detected by NASA’s LIGO/Virgo mission, but had not been fully understood until now.
New simulations show how the collisions influence the spins of black holes, ripping up the stars before eating the stellar debris and becoming more massive.
The additional mass increases their gravitational pull. ultimately realigning their spins in the same direction. Their spin looks like a “googly-eyed heart.”
“This discovery challenges the common belief that black holes formed in star clusters always have randomly distributed spins,” said Kıroğlu.
