Once, in a galaxy far, far away, a black hole swallowed a neutron star. Then, 10 days later, another black hole ate another star. The two separate events triggered ripples across time and space that eventually hit the Earth.
These ripples, first detected in January 2020, provided researchers with two distinct views of previously unmeasured cosmic collisions, according to research published Tuesday in the academic publication The Astrophysical Journal Letters.
“This is the first detection of a merger between a black hole and a neutron star,” said Chase Kimball, a graduate student at Northwestern University and one of the study’s co-authors. “Basically, the black hole is eating the neutron star and getting fatter.”
Astrophysicists previously observed two black holes colliding with two neutron stars in separate events, but the two were never paired together.
“We’ve always thought they exist, but this is the first direct confirmation that will help fine-tune future astrophysical models about binary star systems in our universe and how they interact with each other,” Kimball said.
The collisions and the gravitational waves that followed provide a rare glimpse into how cataclysmic cosmic explosions such as the collision of a black hole and a neutron star affect the expansion and contraction of spacetime – an observation never before seen in the field of gravitational wave astronomy. .
Neutron stars are corpses of large stars 10 to 30 times the mass of the Sun, and black holes are intense regions of space where gravitational forces are too strong for even light to escape. When these astronomical bodies meet, according to Kimball, they orbit each other “like a dance” until they eventually collide and produce a massive explosion.
The merger produces bursts of energy like gravitational waves moving through space and time — a disturbance measured by detectors on Earth from the Laser Gravitational Wave Observatory, known as LIGO.
In collaboration with a smaller detector in Italy called Virgo, LIGO detected the first black hole merging with a neutron star about 900 million light-years from Earth on January 5, 2020. The second gravitational waves were captured far from the star. Planet January 15, 2020.
Since the black hole appears to have swallowed the neutron star almost immediately, Kimball said astrophysicists will need to observe more of this “rare” pairing to learn more about its properties.
“How do they rotate? What exactly is the mass of neutron stars? Why haven’t we observed this in the Milky Way?” He said. “There is a lot to learn.”