enormous Black holes They are some of the most impressive (and terrifying) objects in the universe, with a mass about a billion times greater than that of the Sun. We know they have been around for a long time.
In fact, astronomers It was revealed Extremely luminous compact sources located at the centers of galaxies, known as quasars (fast-growing supermassive black holes), when the universe was less than a billion years old.
Now our new study, published in Astrophysical Journal LettersHe used observations from the Hubble Space Telescope to show that there were many more (less luminous) black holes in the early universe than previous estimates suggested. Excitingly, this could help us understand how they form, and why many of them appear larger than expected.
Black holes grow by swallowing the material around them, in a process known as accretion. This produces huge amounts of radiation. The pressure resulting from this radiation sets a basic limit About how fast black holes grow.
Scientists therefore faced a challenge in explaining these massive early quasars: without a large cosmological time to feed, they must have grown faster than physically possible, or were born surprisingly massive.
Light vs heavy seeds
But how do black holes form at all? There are several possibilities. The first is the so-called Primordial black holes It has been around for a short time after .the big bang. While this is plausible for low-mass black holes, massive black holes cannot form in large numbers according to Standard form Cosmology.
It is certain that black holes can form (now verified by Gravitational wave Astronomy) is in the final stages Of the short lives of some ordinary massive stars. Such black holes could in principle grow rapidly if they formed into very dense star clusters where stars and black holes might merge. They are the “stellar mass seeds” of black holes that must grow very quickly.
The alternative is that they can be formed from “Heavy seeds“, with a mass about 1,000 times greater than known massive stars. One such mechanism is “direct collapse”, where early structures of unknown invisible matter known as Dark matter It trapped gas clouds, while background radiation prevented them from forming stars. Instead, they collapsed into black holes.
The problem is that only a few dark matter halos grow large enough to form such seeds. So this only works as an explanation if early black holes are rare enough.
Lots of black holes
For many years, we have had a good picture of how many galaxies existed in the first billion years of cosmic time. But finding black holes in these environments has been extremely difficult (only luminous quasars have been proven).
Although black holes grow by engulfing surrounding material, this does not happen at a constant rate; they divide their nutrition into “meals”, causing their brightness to vary over time. We monitored some early galaxies for changes in brightness over 15 years, and used that to take a new count of how many black holes there are.
It turns out that the number of black holes in ordinary early galaxies is many times greater than we initially thought.
Other pioneering work has recently begun using the James Webb Space Telescope (JSTW). To reach similar conclusions. In total, we have more black holes than could be formed by direct collapse.
There is another, more exotic way to form black holes that could produce massive, abundant seeds. Stars are formed by the contraction of clouds of gas due to gravity: if large numbers of dark matter particles can be captured during the contraction phase, the internal structure It can be fully modified – Preventing nuclear ignition.
Thus, growth can continue several times longer than the typical lifetime of a normal star, allowing it to become more massive. However, like ordinary stars and directly collapsing objects, nothing is ultimately able to withstand the enormous force of gravity. This means that these “dark stars” must also eventually collapse to form massive black holes.
We now believe that processes similar to these would have had to occur to form the large numbers of black holes we observe in the nascent universe.
Future plans
Early studies Black hole The formation has undergone a shift in the past couple of years, but the field is still somewhat in its infancy.
New observatories in space such as Euclid’s task or Nancy Grace Roman Space Telescopewill fill our population of faint quasars in early times. the Newathena mission and Square kilometer matrixin Australia and South Africa, will open up our understanding of many of the processes surrounding black holes in early times.
But it’s the James Webb Space Telescope that we should be keeping an eye on in the near term. Thanks to its sensitivity for imaging and observation and its spectroscopic capabilities to see very faint black hole activity, we expect the next five years to determine the numbers of black holes as the first galaxies form.
We may even be able to detect black hole formation while watching explosions associated with the collapse of the first pristine stars. Models say this is possible, but it will require a coordinated and dedicated effort by astronomers.
Matthew J. HayesAssociate Professor of Astrophysics, Stockholm University
This article was republished from Conversation Under Creative Commons license. Read Original article.
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