Black Hole and Neutron Star Collision Merge Event: No Detectable Light

BEIJING, May 12 (Xinhua) — Astronomers have so far not observed a black hole colliding with a neutron star, according tomedia reports, and a new study suggests that such collisions release a lot of energy, but surprisingly, may not produce any detectable light. The findings reveal key details about the merger of black holes and neutron stars , which detect the amount of light and the mass of collision objects, and reveal the contributing factors behind the merger, such as the dynamics that contributed to these collisions.

Black Hole and Neutron Star Collision Merge Event: No Detectable Light

  So far, scientists have confirmed that mergers between black holes and neutron stars will occur, and they are looking forward to the first observation of the combination of black holes and neutron stars, a collision that could help validate stellar evolution and Einstein’s general theory of relativity, which is the best description of the gravitational effects of space.

Black holes and neutron stars are the remains of supernovae that have exploded catastrophically, and the explosion of supernovae can briefly brighten a star brighter than all the other stars in the galaxy, and when a star becomes a supernova, its debris core collapses under its own gravity. If the wreck age is large enough, it could form a black hole with a gravitational pull that could not escape light. The smaller cores of stars form neutron stars, and they are named because they have a strong gravitational pull that can crush protons and electrons together to form neutrons.

So far, scientists have confirmed that mergers between black holes and neutron stars will occur, and they are looking forward to the first observation of the merger of black holes and neutron stars, a collision that could help validate stellar evolution and Einstein’s general theory of relativity, which is the best description of the gravitational pull of space.

Researchers have two ways to witness the collision of black holes and neutron stars in two ways: one is that they can look for the types of light or electromagnetic radiation emitted by collisions, such as radio waves, infrared, visible, ultraviolet, X-rays and gamma rays, and that they can survey space-time ripples, known as gravitational waves.

At present, scientists have a complete theoretical framework to explain how neutron stars and black holes formed in the relatively independent state of binary systems collide and merge. Previous studies have shown that a combination of black holes and neutron stars can occur 100 times in a billion-second gap over a year, with a 1 billion-second gap equivalent to a space range of 34.7 billion light-years.

However, when these dead stars are surrounded by dense millions of stars, there is still a lot of uncertainty about their interactions, which can prove to be very different from isolated merging events.

Through 240,000 computer simulations, the combined events of neutron stars and black holes in dense clusters were simulated, focusing on the collision of binary systems and black holes by neutron stars and companion stars, as well as the collision of black holes and companion stars with a neutron star, changing the mass and orbit of all these celestial bodies, as well as the basic properties of other stars in the cluster, such as their elemental composition and speed.

In an unusual discovery, black holes and neutron stars can merge in dense clusters without producing any detectable light, although the merger still produces a large number of gravitational waves. This happens when a neutron star falls into a black hole without turning into a hot, bright fragment, which occurs when the black hole is more than 10 times the mass of the sun — large enough to devour a neutron star.

The difference between the merging events of black holes and neutron stars in dense clusters is that they usually have larger black holes with an average mass of more than 20 times that of the sun. By contrast, according to another study published in the Monthly Notices of the Royal Astronomical Society in 2018, in isolated combinations between black holes and neutron stars, black holes typically have about seven times the mass of the sun and generally no more than 20 times the mass of the sun.

The study suggests that if black holes and neutron star collision events occur in dense clusters, they will have unique properties that scientists can use to distinguish such merge events from isolated merge events. Gravitational-wave observatories such as the European Space Agency’s Laser Interferometer Space Antenna (LISA) may detect such collisions in dense clusters, but one premise is that the furthest cosmic distance from the event is the Andromeda galaxy, the nearest galactic neighbor in the Milky Way. As technology continues to evolve, more advanced gravitational-wave observatories in the future could detect more distant black holes and neutron stars merging events. (Ye Ding Cheng)