No giants live in the heart of the NGC 6397 cluster; Instead, several black holes appear to be clustered together. Two astronomers recently tried to find a massive black hole. They collected a wealth of data from the most powerful telescopes to find any sign of an invisible object hundreds of times the mass of the Sun in a distant star cluster called NGC 6397.
They found a pile full of baby monsters! About 60 black holes: Dark suction motors in space that is hardly larger than our own solar system and propagate their mass in the dense core of this star cluster.
Eduardo Vitral and Gary E. Using data from the Hubble Space Telescope and the European Space Agency's Gala spacecraft, Gary A. Mamon of the Paris Institute of Astronomy published the results of his research on February 11 in the Journal of Astronomy and Astrophysics.
We have found strong evidence of an invisible object in the dense core of this cluster," said Vitral, a graduate student, in a report at the Space Telescope Science Institute. "But we were very surprised to learn that big crime is not a point."
These amazing results provide astronomers with a very unique and partial view of the prevailing dynamics in one of the busiest places in our space. The researchers' work shows that these masses are likely to be the source of gravitational waves that antennas such as LIGO and Virgo have discovered in recent years, resulting from the collision of black holes.
But the discovery raises questions about the complex process that previously existed for the formation of small black holes with masses only a few times that of the Sun, and how they transform into giants that rule or power quasars at the center of galaxies.
As Albert Einstein's theory of general relativity predicts, black holes are objects with such gravity that even light cannot escape them. There used to be doubt about the existence of black holes, but this is not the case now.
There are other black holes with masses several million or billions of times the mass of the Sun that are located in the center of galaxies. There seems to be a correlation between the size of the galaxy and the black hole at its center, but no one knows why or how these giant black holes form.
One idea is that these supermassive black holes are made up of smaller black holes the size of stars, in which case there should be medium-mass black holes - hundreds to thousands of times the mass of the Sun - probably at the center of smaller galaxies or parts of galaxies. But so far no trace of them has been found.
The NGC 6397 cluster is one of 150 spherical clusters of old stars orbiting the Milky Way galaxy that probably existed before its formation. NGC 6397 contains 250,000 stars, all of which are old, small and dim. The big, heavy stars in this cluster have long since come to an end or turned into black holes or other things that happen to a star after death.
So this cluster is probably a good candidate for finding medium-mass black holes. In fact, previous studies have suggested that there is a black hole about 600 times the mass of the Sun at the center of NGC 6397.
To explore this idea, Dr. Mamun and his student looked at data from the Hubble Space Telescope and Gaia from the motion of stars in the cluster. The faster the stars move, the greater the gravitational force, so there must be more mass to hold them in the cluster.
In total, 1,905 stars from the Gaia list and 7,209 stars from Hubble were examined. It turned out that they were definitely under the gravitational force of an invisible object; But instead of orbiting a dark spot, the stars moved in such a way that the mass affecting them did not seem to be concentrated but was actually large. There was no sign of a giant black hole.
"Our analysis found that the rotation of stars, instead of being systematically circular or elliptical, occurs randomly around a mass of mass," says Dr. Mamun.
The motion of these stars is evidence of the existence of a dark mass about 1,800 times the size of the Sun, which is spread over an area one-third of a light-year in diameter. About 40,000 medium-bright, very light-weight stars orbit this space. According to Dr. Mamun, two-thirds of this dark mass is black holes with an average mass of 20 times that of the Sun. The rest of the mass will be the remains of dead stars as well as white dwarfs and neutron stars.
According to these astronomers, it is not clear what will happen next. Accidental collisions of black holes can cause them to lose their mass in the form of gravitational waves. Such compounds will also drive some black holes out of the cluster.
Gravitational interaction with lighter stars within the cluster can cause them to lose speed and be pulled toward the center of the cluster; The process is called "dynamic friction". "This could lead to black holes centering in the center over the next few million years, creating a medium-mass black hole," said Dr. Mannon.
But he also points out that this period of time is nothing compared to the 13 billion years that this cluster existed. So if astronomers could now detect such a short process there, they would be very "lucky". The fact that no medium-sized black holes have formed so far could mean that this will never happen. The concentration of black holes in the center may cause black holes to have very few stars to exchange mass around them, and "this is an obstacle to the formation of a medium-mass black hole."
"The discovery of this concentration of invisible mass in a spherical cluster of nuclear decay is certainly something that forces us to reconsider many of our hypotheses about the formation of medium-mass black holes!"
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