The study of several dozen galaxies within a radius of several billion light-years from our own has revealed several black holes that exceed many times our expectations about how large they can grow. The latest research not only helps us better understand the evolution of these mysterious astrophysical objects, but also opens up new interesting questions for us. For example, how do black holes get so incredibly massive?
Black holes, which are the result of stellar collapse, need no introduction. We have heard that they cause disturbances in space-time, watched their "belching" and even, perhaps for the first time in history, we will be able to see one of them with our own eyes this year. Scientists are very interested in black holes, and there is a very understandable reason for this.
“What are galaxies? These are "bricks" that are combined into the overall picture of the Universe. And to understand how they form and evolve, we first need to understand how black holes work,”says physicist Julia Hlavacek-Larrondo from the University of Montreal, Canada.
Not that black holes themselves simplify this work - it is very difficult to understand what is impossible (as it seems to us) to see directly. Therefore astrophysicists are looking for other clues that would allow them to dig deeper. One of the directions is the search for a connection between the masses of black holes and the galaxies in which they are located. If we had a simple way to compare the size of galaxies with the black holes at their centers, then, according to scientists, this would save us a lot of time and effort to study both the former and the latter.
Therefore, Hlavacek-Larrondo, joining forces with other scientists from Canada, Spain and the UK, conducted a study of 72 galaxies located within a radius of 3.5 billion light years from us, in the hope of coming up with some general formula that could simplify the determination of mass. black holes in galactic centers. Scientists shared their observations in the Monthly Notices of the Royal Astronomical Society.
To estimate the size of the black holes themselves, the team analyzed the X-ray spectrum escaping from the vortex streams of hot gas from the accretion disks of black holes, and then compared the numbers with the overall brightness of the surrounding galaxy.
According to a fairly popular hypothesis, the larger the galaxy itself, the larger the black hole itself, located in its center, can be - but in practice, everything turned out to be not as simple as expected.
“We found that black holes could be much larger than the estimated statutory size,” commented lead study author Mar Mezqua of the Space Science Institute in Spain.
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Instead of the expected correlation in mass and size with their galaxies, a number of black holes have shown much faster growth and mass gain than the rest of the space around them. It turned out that about 40 percent of the investigated black holes have a mass 10 billion or more times the mass of the Sun. Here, however, it should be clarified that no mass records were recorded, and the primacy still belongs to the black hole of the galaxy NGC 4889, whose mass is equivalent to 21 billion solar masses. In addition, there are suspicions that the galaxy S5 0014 + 81, located 12.1 billion light years away, contains a real monster with a mass of about 40 billion Suns. But nevertheless, such a large number of supermassive black holes made scientists wonder how they become such.
Researchers have two assumptions on this score: either these black holes originally appeared very large, and then literally attracted most of the galaxy matter around them, or there are serious gaps in our knowledge of how galaxies produce black holes.
“Are they so big because they immediately appeared like that, or were they helped by ideal conditions that allowed them to grow very quickly for several billion years? We cannot answer this question at the moment,”says Mezqua.
However, the answer to this question may be contained in another study published in the largest online library of scientific papers arXiv.org and pending verification. In its course, scientists studied more than 30,000 galaxies located within a radius of 12.2 billion light years, and found that the ratio of the growth rate of black holes and the growth rate of stars accelerated with the growth of the galaxies themselves, in which the objects under study were located. In other words, in galaxies with a large number of stars, black holes were always "voracious".
A more generalizing takeaway from these studies is that there is indeed a connection between star formation and black holes, and it is very confusing. Of course, more than a dozen more studies will be required in order to better understand it. But one thing is already becoming clear - without these giants, our Universe would look completely different.
Nikolay Khizhnyak