The latest research points out that there may be an intermediate-mass black hole 800 times the mass of the sun in the center of the globular star cluster M4 6,000 light-years away in the Milky Way. Intermediate-mass black holes are still an astronomical mystery, and most of what is known about these intermediate-mass black holes so far is still indirect and uncertain, and the black hole at the center of the M4 globular cluster is no exception. This study uses the Hubble Space Telescope (HST) and Gaia telescope (Gaia) survey data to carefully track the movement of about 6,000 stars in the star cluster. The calculation results show that there may be an intermediate mass 800 times the mass of the sun hidden in the center Black holes, though it’s still not entirely certain.
Astronomers have long identified a considerable number of black holes with extremely extreme mass distributions: stellar black holes less than 100 times the sun, and supermassive black holes millions to billions of times the sun. Between the two extremes, there are hardly any intermediate-mass black holes. Is the universe really devoid of intermediate-mass black holes, or do they exist, but somehow prevent astronomers from detecting them? The astronomical community has understood the cause of the formation of stellar-mass black holes, mainly from the collapse of the core of massive stars or the merger of compact celestial bodies, but there are still many doubts about the formation of supermassive black holes. Is the supermassive black hole formed by the merger of many stellar black holes, or is there another way to form it? Intermediate-mass black holes are an obvious clue, perhaps to the intermediate process in which stellar black holes merge to become supermassive black holes.
ā² The central region of the M4 globular cluster as captured by the Hubble Space Telescope. (Source: NASA)
M4 is one of the closest globular clusters to Earth, and some astronomers speculate that an intermediate-mass black hole may be hiding in the center of the globular cluster. A globular cluster is an extremely dense, spherical-shaped star cluster composed of more than 100,000 to 1 million stars. Most of the stars are formed from the same nebula at the same time. Previous studies on globular clusters have found that the central mass density is quite high, in line with the range of intermediate-mass black holes. Generally speaking, if the black hole is not actively accreting the surrounding matter, it is not easy to find them in general observations, but the clues that the gravity of the black hole affects the orbit of the surrounding stars are quite reliable.
The research team calculated various models to rule out the possibility that many black holes gathered in the center of the star cluster, and also confirmed that there is a large amount of mass concentrated in a small area. Although it is still not completely sure that it is caused by the gravity of a single celestial body, it can be proved that it is very, very small. In the absence of entirely new unknown stellar types or unknown astrophysical explanations, intermediate-mass black holes are the most likely explanation. The researchers recommend continuing to observe more of the M4 globular cluster with the Hubble and Webb Space Telescopes to determine how the stars move in the cluster. The research will be published in the July Monthly Notices of the Royal Astronomical Society (MNRAS).
(This article is reproduced with the authorization of Taipei Planetarium; the first picture is the M4 globular cluster in Scorpiusļ¼Source: ESO)
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