In the middle of galaxies such as the Milky Way, are supermassive black holes. Their mass ranges from 1 million to 10,000,000 solar masses. It is harder to find their smaller brothers, intermediate-mass blackholes (IMBH), which range between 100 and 100,000 solar masses.
Astronomers discovered a black hole of intermediate mass that was destroying a star too close to it. These black holes have been a source of great learning for the team. They hope to continue their research and find more. Observing more black holes may help to understand how SMBHs became so large.
A tidal disruption (TDE), occurs when a star is too close to a black hole. The star is torn into pieces and its constituent material is drawn to the black holes, where it is trapped in the holes accretion disc. This event releases a tremendous amount of energy that outshines all other stars in the galaxy for many months or even years.
This is what happened to TDE 3XMM J215022. Astronomers could only spot the mysterious IMBH due to the bursts of x-rays that were emitted from hot gas as the star was being torn apart. J2150 lies 740 million miles from Earth, in the direction the Aquarius constellation. A team of scientists has now used observations from J2150, as well as existing scientific models, to find out more about the IMBH.
Sixiang Wen, from the University of Arizona, is the lead author. The paper was published in The Astrophysical Journal.
We were able capture the invisible black hole as it devoured a star, which is a remarkable opportunity for us to observe what would otherwise be hidden.
IMBHs can be difficult to find and are difficult to study. Numerous IMBHs have been found in the Milky Way and nearby galaxies by astronomers. They are most often spotted due to their low-luminosity active gallactic nuclei. The LIGO and Virgo gravitational waves observatories spotted a gravitational signal from the merger between two IMBHs in 2019. As of now, scientists have only identified 305 candidates for IMBHs, despite the possibility that they may be common in galactic centers.
Their low mass is one of the difficulties in seeing them. While SMBHs can often be identified by observing the stellar dynamics of nearby stars affected by their mass, IMBHs are usually too small to do so. Their gravity is not strong enough to alter the orbits of nearby star stars.
Ann Zabludoff (UArizona professor in astronomy, co-author of the paper) said that being able to capture this black hole as it was devouring a star is a remarkable opportunity to observe something otherwise invisible. We were also able to understand the mysterious category of black hole by analysing the flare, which could explain the majority of black holes found in the centers galaxies.
This Hubble image shows J2150 within the white circle. It is located in a dense cluster consisting of stars, approximately 740 million light years away. The IMBH was detected using X-rays from the TDE, but its location was determined by Hubble's visible-light capabilities. Image credit: NASA, ESA and D. Lin (University of New Hampshire).
The event was made visible by the X-ray eruption. The team compared the observed and predicted x-rays to models, and confirmed the existence of an IMBH. Wen, the lead author, said that the X-ray emission from the inner disk made by the debris and dead stars allowed us to infer the mass of the black hole and classify the black hole as an intermediate one.
It is the first time observations have been sufficiently detailed to allow us to use a TDE flare in order to confirm the existence of an IMBH. This is a significant accomplishment, as we know that SMBHs are located in the middle of galaxies such as the Milky Way, but our knowledge of smaller galaxies with their IMBHs and SMBHs is limited. It's just very difficult to see them.
Peter Jonker, co-author of Radboud University and SRON Netherlands Institute for Space Research in the Netherlands, stated that we still don't know much about the existence black holes in the center of galaxies smaller then the Milky Way. It is difficult to find central black holes smaller than 1,000,000 solar masses due to limitations in observational data.
The mystery surrounding IMBHs is mirrored in the mystery surrounding SMBHs. Although we can see SMBHs in large galaxies, we don't know how they got so massive. Perhaps they were involved in mergers. Perhaps. Through the accretion and decomposition of matter Perhaps. Most astronomers agree that both mechanisms could play a part.
Another question is about SMBH seeds. These could be IMBHs with tens to hundreds of solar masses. It is possible that the IMBHs could have grown from stellar-mass black hole remnants, which grew into IMBHs by the accretion matter. There is another possibility that large gas clouds were formed long before stars were created. These quasi-stars then became black holes. These bizarre entities are called direct collapse black holes. They would fall directly from a quasi-star to a black hole, without ever becoming stars. These are just hypotheses. To confirm or rule out anything, astronomers need more concrete observations, such as in the TDE J2150 case.
Jonker stated that if we have a better understanding of the number of bona fide intermediate dark holes out there, it will help us determine which theories about supermassive blackhole formation are correct.
The artists illustration shows what astronomers refer to as a "tidal disruption events" (or TDE). This is when an object, such as a star, wanders too close a black hole, and is destroyed due to the tidal force generated by black holes' intense gravitational forces. (Credit: NASA/CXC/M.Weiss.
Researchers were also able measure black holes' spins, which could have implications for black hole growth and particle physics. Although the black hole is spinning fast, it's not spinning as fast. This begs the question: How did the IMBH achieve such a high speed? The spin opens up new possibilities and eliminates old ones.
It is possible that the blackhole formed in this way and hasnt changed since then, Zabludoff stated. The spin measurement excludes any scenario where the black hole is growing slowly from gas intake or quick gas snacks.
The spin rate could also shed light on possible particle candidates for dark matter. One hypothesis is that dark matter may be made up of ultralight bosons, particles which have never been seen in a laboratory. If they are real, these exotic particles would be one-billionth of the mass as an electron. These candidate particles may not exist due to the IMBHs spin rate.
Nicholas Stone, co-author, stated that if these particles exist and have masses within a specific range, they will stop an intermediate-mass blackhole from spinning fast. But J2150s black holes are spinning very fast. Our spin measurement rules out many ultralight boson theories. This highlights the importance of black holes being extraterrestrial laboratories for particle Physics.
This will lead to a better understanding and appreciation of dwarf galaxies as well as their black holes. However, for this to happen, astrophysicists must observe more IMBH disruption events.
Stone stated that if it turns out that many dwarf galaxies have intermediate-mass black hole, then this will increase the rate of stellar disruption. Wen said that by fitting the Xray emission from these flares with theoretical models, it is possible to conduct a census on the intermediate-mass population of black holes in the universe.
Future observatories and telescopes should be able to expand our knowledge, as is the case with astronomy, astrophysics and cosmology. The Vera C. Rubin Observatory might play a part in this. The Rubin could uncover thousands of TDEs every year.
Then, we might finally be able piece together the story not only of IMBHs, but also SMBHs.
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