Using the Hubble Space Telescope, astronomers have discovered a massive black hole, the closest thing to Earth so far: a cosmic giant frozen in time.
Meanwhile, the newly discovered intermediate-mass black hole is a spectacular collection of about 10 million stars. Omega Centauri It is located about 18,000 light years from Earth.
Interestingly, the fact that the “frozen” black hole appears to have inhibited growth supports the idea that Omega Centauri is the remnant of an ancient galaxy. Devoured by our galaxy.
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This suggests that Omega Centauri is actually the center of a small, independent galaxy whose evolution was interrupted midway. milky way If this event had not occurred, the intermediate black hole might have grown to a supermassive mass, like the supermassive black hole in our galaxy. Sagittarius A* (Sgr A*) has a mass 4.3 million times that of the Sun and is located 27,000 light years from Earth.
Finding what’s lost
Scientists have known for some time that not all black holes are created equal. Stellar-mass black holes Star Collapse Supermassive black holes, which have masses more than eight times that of the Sun, must have a different origin because no stars are massive enough to collapse and leave behind debris. Millions It has many times the mass of the sun.
Therefore, scientists Supermassive black holes are born and grow This is due to a chain of mergers of increasingly larger black holes, as evidenced by the detection of ripples in space-time. Gravitational waves emanating from Black hole merging.
This process of black hole merging and growth, combined with the large difference in mass between stellar-mass and supermassive black holes, means that a population of intermediate-sized black holes should exist.
An illustration showing the three types of astrophysical black holes, the most massive on the left and the least massive on the right. (Image courtesy of Robert Lea, created using Canva)
But these intermediate-mass black holes, with masses hundreds to thousands of times that of the Sun, seem to have largely eluded detection. That’s because, like other black holes, these mid-sized cosmic giants Event Horizon .
What is the event horizon? Gravitational effects of black holes Black holes become so massive that even light cannot escape them fast enough. Therefore, the only way black holes are visible in the light is if there is food material around them that heats up and glows, or is called a “glowing black hole.”“Tidal Disruption Event” (TDE).
Neutral black holes, like the one in Omega Centauri, aren’t surrounded by much matter or nourishment.
This means astronomers have to get a little crafty in their search for black holes, taking advantage of the gravitational effects they have on matter, such as the stars orbiting them and the light that passes through them. The team behind this new discovery used the former method.
Galloping Star
The search for this intermediate black hole began in 2019, when Nadine Neumeyer from the Max Planck Institute for Astronomy (MPIA) and Anil Seth from the University of Utah designed a research project to improve our understanding of Omega Centauri’s formation history.
In particular, researcher and collaborator MPIA doctoral student Maximilian Hebel, Rapidly moving stars Omega Centauri provides evidence that the cluster has a massive, dense, or compact, “central engine” black hole. A similar method was used to determine the mass and size of Sgr A*, a fast-moving star cluster at the center of the Milky Way galaxy.
Hebel and his team have more than 500 Hubble Images Observations of the cluster built up an extensive database of the motions of stars in Omega Centauri, measuring the velocities of around 1.4 million stars. These repeated observations of Omega Centauri, carried out by Hubble for instrument calibration rather than out of scientific curiosity, were an ideal data set for the team’s mission.
“Finding a fast star and recording its motion is like looking for a needle in a haystack,” Hebel said. Seven They are “stars searching for a needle,” moving at high speed through a small region at the center of Omega Centauri.
Moving on to Sagittarius A*, there is another massive black hole close to Earth. (Image courtesy of EHT Collaboration)
The high speeds of these stars are caused by concentrated mass nearby. If the team found only one fast star, they would be able to determine whether its speed was due to a large nearby central mass or whether the star was run away It has no central mass and travels at high speed in a straight line path.
They were able to make this determination by observing and measuring the differences in speed and direction of seven stars. The measurements revealed a central mass equivalent to 8,200 suns, but visual inspection of the area did not reveal any star-like objects – exactly what would be expected if the region contained a black hole. The team determined that the region is “a light month” wide.
The fact that our galaxy has matured enough to have developed a supermassive black hole at its center means that galaxies have probably passed the stage where they host many intermediate-mass black holes, such as the one in our Milky Way, the team said. Cannibalism of the original galaxy It just so happened that growth process was suppressed.
“Previous research has raised an important question: ‘So where are the fast-rotating stars?’ We now have the answer and confirm the presence of an intermediate-mass black hole in Omega Centauri,” Hebel said. “At a distance of about 18,000 light-years, this is the closest known example of a supermassive black hole.”
Of course, this doesn’t actually change Sgr A*’s status as the closest supermassive black hole to Earth, or Gaia BH1’s status as the closest stellar-mass black hole to Earth, but it does provide some reassurance that scientists are on the right track when it comes to considering how the black hole at the center of Earth became such a cosmic giant in the first place.
The team’s research was published Wednesday (July 10) in the journal Nature.
