Could a black hole binary star with a total mass 28 billion times the mass of the Sun provide an idea for solving a particular problem? | sorae universe portal website

It is believed that there is a “supermassive black hole” at the center of almost all giant galaxies, and some of these galaxies have masses as massive as tens of billions of the mass of the Sun. These black holes are thought to have been created by the merger of smaller black holes, but given the mechanism,Black holes that shouldn't merge, merge“I'm having a strange contradiction. This is it.”The ultimate parsec problem” he is called.

A research team led by Tirth Sorti of Stanford University has discovered that active galaxies exist4c+37.11(B2 0402+379)'' He analyzed the properties of a supermassive black hole. As a result, the supermassive black hole at the center of 4C+37.11 is…The total mass is 28 billion times the mass of the SunI discovered that it is. In the heart of 4C+37.11The black holes are only 24 light-years away from each otherThis is known from previous research. The mass is unprecedented for a black hole binary so close together, and 4C+37.11 is an “important fossil of a galaxy cluster” for exploring its formation process and providing clues to the ultimate parsec problem. .

■The “ultimate parsec problem” for black holes that cannot merge

In the middle of a huge galaxy like the Milky Way, there is…Giant black hole“It is believed to exist. Although their mass is small, they are millions of times greater than the mass of the Sun, and some are estimated to be tens of billions of times larger. A black hole is created when the center of a massive star collapses, but this process only results in a black hole of It is only a few tens of times the size of the Sun, regardless of how heavy it is, so black holes must repeatedly merge to form a supermassive black hole.

Because the universe is so vast, even when black holes get close to each other, they never collide head-on, and in most cases simply pass past each other. For black holes to collide with each other, they must enter binary orbits around each other, and their orbits must contract until they eventually reach zero.

A process called “dynamic friction” is responsible for the formation of binary stars between black holes that collide with each other, and for their orbits to eventually become smaller. If there was a third object other than the two black holes, the orbits of the three objects would change during the close encounter. At this time, when the kinetic energy is transmitted to the third celestial body, the black hole slows down, while the third celestial body accelerates and explodes outward. Black holes that have slowed down may turn into binary stars, or their orbits may become smaller. This is called dynamic friction because gravity reduces the speed of movement as if it were a frictional force.

However, for dynamic friction to occur in a very massive object such as a supermassive black hole, a very large amount of material such as a star or interstellar gas is required as a third object. Dynamic friction simulations show that stars and stellar gas, the material that transfers kinetic energy from the decelerating black hole, are exhausted, and when the distance between black holes becomes from several light-years to several tens of light-years, they encounter a wall where dynamic friction stops and the orbit does not shrink.

In this case, the only process by which a supermassive binary black hole can shrink its orbit is by reducing its energy by emitting “gravitational waves.” However, such a process becomes noticeable only when they are only a few hundredths of a light-year apart (several tens of billions of kilometers), and is ignored in black hole binaries more than a few light-years apart. It will be as small as possible.

As a result, in theory, supermassive black holes should never merge, even over a period of time similar to the history of the universe. However, there are many supermassive black holes in the actual universe, and…Black holes that shouldn't merge, merge“, so this problem seems to be solved in some way. Since the unsolved distance of the representation is several parsecs (one parsec equals about 3.26 light-years), this unsolved problem isThe ultimate parsec problem” he is called.

■It turns out that the binary black hole “4C+37.11” is very large

To solve the ultimate parsec problem, we need to detect supermassive black holes just before they merge and closely monitor their environments.

Surti and his team analyzed archives of observational data from the Gemini North telescope, located atop Mauna Kea in Hawaii, and found that active galaxies are…4c+37.11We have performed an analysis of the supermassive black hole located in “. 4C+37.11 had been attracting attention even before this research, and in 2006 it was revealed that the supermassive black hole is very close by, only about 24 light-years (7.3 parsecs) away.

Surti and his colleagues used the spectrometer installed on the Gemini North telescope.Genetically modified organisms(Gemini Multi-Object Spectrograph)'' and calculate the mass of the supermassive black hole at the center of 4C+37.11. By analyzing the light reaching Earth from the galaxy in detail at each wavelength, we can measure the speed of the star at the center of the galaxy, and from that we can determine the total mass of the black hole binary at the center.

As a result, the binary black hole 4C+37.11 isThe total mass is about 28 billion times the mass of the Sun.It has been calculated. This value is one of the largest known black hole binaries.They are very close to each other at a distance of 24 light years.Given this, the binary black hole 4C+37.11 is very noteworthy.

■4C+37.11 is the solution to the final parsec problem

It is estimated that some black hole binaries orbit each other at a distance closer than 4C+37.11, but this has not been proven observationally, so4C+37.11 is the smallest and largest black hole binary in realityYou will become. Also, due to the binary star's large size, it is estimated that 4C+37.11 has already experienced a merger several times. In other words, 4C+37.11 was a collection of multiple galaxies.Galaxy cluster fossil“It can be considered.

It is estimated that the binary black hole 4C+37.11 has not become closer together for at least 3 billion years. It is not known whether they will remain stagnant forever after that, or whether they will accumulate within a few million years (in an instant in astronomical terms). Given that 4C+37.11 is a “fossil galaxy cluster”, it is unlikely that dynamic friction will resume due to the addition of material. (※).

Surti and his colleagues plan to monitor the state of the center of 4C+37.11 and check how much gas and other materials are present. A more detailed understanding of the environment of 4C+37.11 may provide important clues in determining whether binary black holes can merge and overcome the ultimate parsec problem.

*…As a solution to the ultimate parsec problem, a process has been proposed in which another supermassive black hole, gas, or other matter is added and dynamical friction is restarted. However, although such a process occurs when galaxies merge, 4C+37.11 has already completed its merger and is isolated, so such an event cannot be expected.

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Written by Riri Aya