How many in the universe black hole ？
According to a new study, in the universe as a whole Baryon About 1% of the matter is locked in a black hole with stellar mass. Surprisingly, the researchers also estimated that, At present, the number of black holes in the observable universe is about 400000000000000000 。
In the past few years, major breakthroughs have been made in the field of black holes. We have not only directly detected black holes for the first time, but also Gravitational wave , also took a real picture of the supermassive black hole at the center of the galaxy.
But there are still too many things we don't know about black holes. One of the biggest mysteries is that, How did they form in the first place 。
Recently, a group of research teams believed that they had observed this process. Researchers have observed a kind of unusual cosmic explosion, which can provide some clues to what happens when black holes form. The research results have recently been published in two papers in Nature and Astrophysical Journal.
Black hole formation theory
For most of a star's life, the outward pressure generated by its core nuclear fusion reaction will compete with the inward gravity to keep the star stable. However, once the star runs out of fuel and the nuclear fusion reaction stops, gravity will take the upper hand. The inner layer of a star It will collapse inward under the action of gravity and squeeze to an extraordinary density.
Most of the time, this catastrophic collapse stops when the star's core condenses into a solid ball rich in neutrons. This led to a powerful rebound explosion that destroyed the star, which is also called Supernova explosion ， Finally, we left one called neutron star A strange celestial body.
But if the initial star mass is large enough ， The collapse will continue until the star is compressed into a gravitational singularity and a black hole is formed 。
Although the process of star collapse to form a neutron star is often observed in the whole universe, astronomers are not completely sure what will happen when the star collapses to become a black hole.
Some pessimistic models show that the whole star will be swallowed up, leaving almost no trace. However, others have suggested that the process of collapsing into a black hole will produce some other types of explosions. For example, if the star is rotating while collapsing, some materials falling inward may be concentrated to escape the star at a high speed Jet Medium. Although these jets do not contain much mass, they can bring great impact. If they hit something, the impact may be quite huge in terms of the energy released.
If we can find some clues from the observed similar bursts, we may have a better understanding of the process of black hole formation. This is also the goal of astronomers.
Best Candidate Phenomenon
So far, the best candidate phenomenon for black hole explosion is a phenomenon called Long term gamma ray bursts The strange phenomenon of.
Such incidents were first discovered by military satellites in the 1960s. Scientists speculate that this phenomenon is caused by the newly formed black hole in the collapsed star accelerating the jet to an incredible speed.
However, there has always been a problem with this scenario, that is, gamma ray bursts will also emit a large number of radioactive debris that will continue to shine for months. This shows that most of the stars seem to explode into space (Like ordinary supernovae) Instead of collapsing inward into a black hole. Although this does not mean that black holes cannot form in such explosions, some researchers believe that there should be a more natural explanation. For example, a super magnetized neutron star may form in such an explosion and generate a strong jet.
Now, new research has recently found a (In their opinion) New candidate events to better create black holes. In 2019 and 2021, the research team observed two galaxies about 1 billion light years away An unusually fast and transient explosive type They are derived from a small amount of extremely fast moving material that violently impacts the gas in its adjacent environment.
Such outbreaks are very difficult to study because they occur in a short time, so they are often called Temporary source , which is very difficult to find in the whole universe.
In the past few years, scientists have had to use several observatories consecutively to describe the characteristics of these eruptions, including Zweiki Transient Facility Find them, use the Liverpool Telescope and the Nordic Optical Telescope to confirm their properties, as well as large and high-resolution observatories (Hubble Space Telescope, Gemini Observatory and Very Large Telescope) To analyze their composition.
The team passed spectroscopy , a technique that breaks light down into different wavelengths, and they infer the composition of the exploding stars in each event.
It was found that these spectra were Wolf Rayet (WR type star) Very similar. This is a class of extremely massive and highly evolved stars, so the two astronomers who first discovered them Charles Wolf （Charles Wolf） and George Rayet （Georges Rayet） Naming.
The exciting thing is These results can even help researchers rule out the possibility of a "normal" supernova explosion. The results show that once the collision between the fast-moving substance and the environment stops, the light source will actually disappear rather than continue land luminescence. In this case, Exactly During the collapse of the star core, the star only ejects a small amount of material, and the rest of the material collapses inward into a huge black hole.
Is not the only possibility
Although the research team is currently inclined to believe that this may be a phenomenon that occurs during the formation of black holes, it is not the only possibility.
For example, the most "boring" possibility is that this is an ordinary supernova explosion, but a huge dust shell was formed in the collision, hiding radioactive debris out of the field of vision. Another possibility is that this explosion is a new type that we are not familiar with, originating from stars that we are not familiar with.
In order to answer these questions, scientists need to find more such objects, and more data from similar events may soon help verify or falsify this hypothesis. They can also help determine the link between these events and other types of unusually rapid outbreaks.
In any case, scientists believe that we seem to have ushered in the era of starting to solve the mystery of black holes.
#Creative team:
Original author: Daniel Perley (lecturer in astrophysics at Liverpool John Moores University)
Compiled by: M ∨ ka
Typesetting: Wen Wen
#Reference source:
https：//theconversation.com/black-holes-we-think-weve-spotted-the-mysterious-birth-of-one-174726
https：//www.eurekalert.org/news-releases/940381
#Image source:
Cover/ First picture: principle
