Black holes are perhaps the strangest and most mysterious objects in the known universe. No one has seen them, but scientists are sure that they exist. They are not only predicted by Einstein, their presence is indirectly confirmed by the influence they have on the space-time around them. We do know something about these objects, but we do not know even more. According to scientists, understanding the phenomenon of black holes and, in particular, those processes that occur in their centers, will allow us not only to understand, but also give us the opportunity to control the very fundamental forces of nature, for example, the same gravity.
Every year, scientists report discoveries related to black holes, step by step, leading to a closer understanding of their nature. Today we'll talk about the ten most recent.
Many black holes of intermediate mass
Among the family of black holes, perhaps the most prominent are the so-called medium (or intermediate) mass black holes. These are black holes, the mass of which is significantly greater than the mass of stellar-magnitude black holes (from 10 to several tens of solar masses), but much less than that of supermassive black holes (from a million to hundreds of millions of solar masses). Previously, it was assumed that this type of black hole occurs much less often than the other two classes indicated, but a recent discovery refuted this opinion.
In 2018, scientists found a place where such objects are most often found. For unexplained reasons so far, medium-mass black holes are most often found in the centers of small galaxies. Once scientists figured it out, the rare black hole was no longer rare. Moreover, this discovery may help solve another mystery associated with black holes.
One of the most pressing questions of modern astronomy is the nature of supermassive black holes. Scientists cannot understand how some of the discovered supermassive black holes in relatively compact galaxies have grown very quickly in size since the Big Bang. Those same medium-mass black holes can point to the correct answer. According to one of the assumptions, supermassive black holes could have grown from black holes of average mass, according to another - they were born that way from the very beginning. But how? Scientists cannot yet provide an exact answer, but it seems that they are starting to move in the right direction.
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Mysterious objects near Sagittarius A *
Sagittarius A * is a supermassive black hole located in the center of our galaxy. In the early 2000s, scientists discovered two mysterious objects next to it. They were nicknamed the G-class objects and were originally mistaken for gas and dust clouds. The mystery began after these objects approached the black hole. Instead of being torn apart by the powerful gravity of a supermassive black hole, objects G1 and G2 were somehow able to survive.
In 2018, scientists discovered three more G-class objects (G3, G4, G5) near Sagittarius A *. Analysis of the data collected over 12 years has not finally clarified the picture for astronomers. Objects attract attention for their unusual properties. All five G-objects have the characteristic visual signatures of gas clouds, but behave like stars of enormous mass.
Based on this, scientists have made the assumption that they encountered a very rare type of stars, uncharacteristic for our galaxy. Scientists explain the appearance of these objects by the unique conditions in the vicinity of a supermassive black hole: here, under the influence of powerful gravity, binary stars can collapse to form a single, large object enveloped in thick gas and dust envelopes. Nevertheless, scientists note that not all objects have similar orbits around a black hole, so they cannot yet explain the nature of the phenomenon they saw.
The oldest black hole
The discovery of the oldest black hole is not just a matter of age. The discovery of this old man can help us solve many interesting mysteries associated with the era when the first stars in the universe just began to ignite.
According to scientists, the black hole ULAS J1342 + 0928 discovered in 2017 was born only about 690 million years after the Big Bang. When the cosmos was only 5 percent of today's age, this black hole was already 800 million times the mass of our Sun today.
The object is located about 13.1 billion light years from Earth and formed during the early days of the universe. This period is often called the era of reionization, when the first stars, galaxies, clusters and superclusters of galaxies began to appear due to gravitational attraction. The full picture of reionization is still not clear to scientists, so the black holes that appeared during this period may certainly be one of the most interesting sources of new information.
As noted above, scientists also cannot understand how in such a short time after the Big Bang, black holes were able to accumulate a huge amount of mass. Objects like ULAS J1342 + 0928 may shed light on this question, but in order to draw some conclusions, it would be nice to find at least a few more similar space dinosaurs. Unfortunately, black holes of the era of reionization are extremely rare.
Fastest growing black hole
In 2018, scientists discovered the "hungry" black hole in the known universe. Every day, every second, it consumes a mass equivalent to the mass of our Sun, due to which it also grows rapidly. Luckily for us, she is very far away. If this monster were in the center of the Milky Way, then the X-rays it creates would sterilize the Earth from any life.
When scientists discovered the first light from the quasar J2157-3602 associated with this black hole, its age was estimated at 12 billion years. As soon as scientists confirmed that there really is a black hole next to the quasar, its mass was already about 20 billion solar masses. At the moment, astronomers cannot explain the reason for the rapid growth of the black hole.
The only thing that is known about this object is that its appetites heat the surrounding gas and dust to such a state that their brightness will easily overshadow the light of almost all stars in the sky.
Hidden cluster
One galaxy cluster can contain hundreds or even thousands of galaxies. These clusters are regarded by scientists as some of the largest objects in the universe. Do you think such a whopper is impossible to hide with a single space object? You are wrong. One quasar proved otherwise.
The discovered object was named PKS1353-341 and was originally meant to be a separate galaxy, with an incredibly bright central region. However, astronomers at the Massachusetts Institute of Technology in 2018 discovered a truth that had been hidden for several decades since the object was discovered. It turned out that the object is not a galaxy, but one single quasar (a region of hot gas surrounding a supermassive black hole), which is located in the center of an entire galaxy cluster located 2.4 billion light-years from Earth.
The quasar was so bright that it literally eclipsed the entire surrounding space containing hundreds of galaxies. Scientists from MIT calculated its brightness and it turned out that it is 46 billion times brighter than the Sun. According to the researchers, such extreme brightness is associated with the absorption of a large amount of surrounding material by the central supermassive black hole.
Dual systems
Another mystery for scientists is the so-called double, that is, paired black holes that wrap around each other. Cases of collisions of black holes have already been noted by scientists in the past. Two were identified in 2015, and one more in 2017. Surprisingly, thanks to the latter, scientists for the first time became direct witnesses of an equally rare phenomenon.
The signal received from the collision of two black holes showed signs of gravitational ripples in space-time - changes in the gravitational field, propagating like waves. In this case, both black holes were not destroyed, but instead merged into a single whole - a supermassive black hole, even larger in size than its progenitors.
Scientists have two assumptions about the nature of the appearance of systems from binary black holes. According to one, binary black holes appear when binary star systems die. According to the second, black holes are formed independently of each other and after that, drifting in space, they are attracted to each other under the influence of gravitational forces.
Deadly bubble
In 2018, physicists suggested another scenario of the apocalypse: the Earth could be destroyed by black holes. A year earlier, the scientific world celebrated the confirmation of the discovery of gravitational waves, a phenomenon that stretches and contracts the fabric of reality. This power is deadly.
In the new theory, scientists from Princeton University predicted one of the scenarios of what could happen if, as a result of high-energy cosmic cataclysms (for example, when two black holes or two neutron stars merge), the resulting gravitational waves collide with each other.
For illustration purposes, gravitational waves are often compared to the circles in the water that occur when a stone is thrown. However, if a particle or object moves at the speed of light, plane gravitational waves can appear. According to scientists, if the waves are large enough, then their collision could create a giant black hole that will change space and time over a huge area of outer space.
If this happens next to the Earth, then not only all living things, but also the planet itself and the entire solar system will come to an end.
Rogue Black Hole
Scientists have repeatedly wondered about the possibility of galaxies "ejection" of their central black holes. However, for a long time, astronomers could not find evidence of this phenomenon. But in 2017, the galaxy 3C186 presented space explorers with a real surprise.
According to scientists, earlier the galaxy 3C186 was two separate galaxies, which at some point in their history merged into one. The new galaxy took on quite clear outlines and shape, instead of the alleged disorderly structure, but the main surprise came from its center: scientists, full of hopes of finding a supermassive black hole in it, did not find anything at all.
Later, the black hole was still discovered, only 35,000 light years from the galactic center 3C186. When the two star clusters collided, their central galactic black holes collided, eventually creating a supermassive black hole. This event most likely created very powerful gravitational waves that pushed this newly formed black hole out of the galaxy, scientists explain.
This, however, turned out to be not so easy, the researchers continue. The ejection of a black hole from the galactic center required energy equivalent to the explosion of 100 million supernovae. Scientists still have not figured out what actually happened there, but it is already becoming clear that there are forces that can withstand even the power of the black holes themselves.
Interestingly, the rogue black hole continues to move towards the edges of its galaxy. At the current rate, it will be completely ejected outside of it in about 20 million years.
Reverse time
Black holes form when a gravitational collapse (compression) of a sufficiently massive star occurs, or the collapse of the central part of the galaxy or protogalactic gas. At this moment, a colossal amount of gamma radiation is thrown into space. The latter, in turn, is the brightest electromagnetic event occurring in the Universe and is still not fully understood by scientists.
In 2018, very strange signs were found in the captured gamma-ray signals, which, according to researchers from NASA, can be interpreted as "time reversal." Typically, every gamma-ray event emits a signature waveform that never repeats. The detected signals contained anomalies that, as it turned out, could not be explained from the standpoint of any theoretical model. These signals were special wave-like structures that were rotated in time as if their beginning was at the end of the burst, and the end - in the first moments of the burst.
For some physicists, such an observation was enough to claim evidence of the reversal of time. According to another and, most likely, more realistic explanation, the rays of the gamma-ray emission on their way could collide with some matter, which endowed the waves with a signature that was accepted by scientists for the reverse course of time. It is quite possible that the rays hit some kind of accumulation of matter, which acted on them like a reflecting surface. Nevertheless, the possibility is not excluded that we are talking about a completely new law of physics, the first example of which was scientists in 2018.
Ghosts of lost universes
In August of this year, the British physicist at Oxford University Roger Penrose made a very loud statement. He and his team argue that before the advent of our universe, that is, before the Big Bang, there was another universe. This conclusion was prompted by a series of observed light anomalies in the microwave background radiation, which, according to Penrose, are light spirals left over from black holes that belonged to the previous universe, which existed before the Big Bang.
In one of his theories, the even more famous British physicist Stephen Hawking suggested that black holes, after losing the bulk of their particles, disappear. These hypothetical particles are called gravitons. They have no mass, no electric or other charge, but at the same time they have energy and therefore participate in the gravitational interaction.
When one universe dies and a new one appears, these gravitons, according to Penrose, become part of the new universe. The scientist and his colleagues are convinced that they found these surviving "remnants" in the microwave background radiation. They called the detected light anomalies "Stephen Hawking's points." If the observations of scientists are confirmed, we will face a serious revision of the Big Bang theory.
Nikolay Khizhnyak