Talk about heavy treats. For the first time, astronomers instantly witnessed a black hole swallowing a neutron star, the densest object in the universe.
Ten days later, they saw the same thing on the other side of the universe. In both cases, the neutron star (a teaspoon weighs 1 billion tonnes) gets even closer to its final non-returning point, the black hole, until it finally collides and the neutron star wobbles.
Astronomers have witnessed the last 500 orbits before the neutron star was swallowed. This process quickly generated the same amount of energy as all visible light in the observable universe in less than a minute.
Patrick Brady, an astrophysicist and co-author of the study at the University of Wisconsin-Milwaukee, said: The black hole “has a nice neutron star supper and makes itself a little bigger.”
The burst of energy from the collision was discovered when a detector on Earth discovered the gravitational wave of the merger, the energy ripple of the universe soaring in space-time as first theorized by Albert Einstein. They each came from over a billion light-years away. The wave was detected in January 2020, but a study by more than 100 scientists on the analysis and interpretation of data was published in the Astrophysical Journal Letters on Tuesday.
Astronomers have seen gravitational waves from two black holes collide with each other and two neutron stars collide with each other, but this is the first time they have seen one of each collide.
Neutron stars are giant corpses of stars that remain after the death of a large star in a supernova explosion. They are so dense that they have about 1.5 to 2 times the mass of our Sun, but they are condensed to about 6 miles (10 km) wide, Brady says. Some black holes, called stellar black holes, are created when a larger star collapses, creating something with such a strong gravity that even light cannot escape.
Scientists believe there should be many combinations of these neutron stars and black holes, but we haven’t found them in our own galaxies yet.
“This is very cool,” said Mark Kamionkowski, an astrophysicist at Johns Hopkins University who was not part of the study. He said this would help astronomers predict how abundant these combinations would be.