The discovery was made inside a cluster of stars in the Andromeda Galaxy, known as the AKA M31. Experts studied changes in light to identify a vast area of space-time nearly 100,000 times the mass of the Sun. It places it in the “intermediate mass” bracket of black holes – both elusive and much sought after by astronomers to answer the universe’s biggest questions.
The team of astronomers, led by Renuka Pechetti of Liverpool John Moore’s University, wrote: “In this paper, we use high-resolution mass models and kinematics to present the detection of a ~ 100,000 solar mass-medium black hole (IMBH) with a larger than 3-sigma importance.”
Their work has been submitted to the preprint server arXiv and accepted for publication by the American Astronomical Society (AAS).
Black holes form when massive stars collapse at the end of their lives and can continue to grow by absorbing and merging with others.
This interaction has been observed for decades, and scientists use it to identify their presence as radiation is emitted as visible light across space.
Most black holes can be categorized by two mass areas.
There are the black holes with star mass, up to about 100 times the mass of the Sun; and supermassive black holes, which start at a low area of about a million times the mass of the Sun.
In the middle, a series is classified as intermediate, and although their detection helps provide the “missing link” to the secrets of the universe, it is extremely rare.
To date, the number of IMBH detections remains incredibly low.
Without more black holes with intermediate mass, scientists are struggling to figure out how two wildly different mass regimes can exist side by side.
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A solid population of black holes in the mid-mass area could help us bridge the gap and offer a mechanism by which black holes with star mass can grow into giants.
That’s why a cluster of stars in the Andromeda Galaxy, known as B023-G078, is so interesting to scientists.
B023-G078 is the most massive such star cluster in the galaxy, an approximately spherical, gravity-bound cluster of stars that clock in at 6.2 million solar masses.
One way these clusters can form, according to models, is when one galaxy subsumes another.
And that’s what the team thinks has happened to B023-G078.
They examined the metal content of the cluster, based on subtle signatures in the light it emits, and determined that it is about 10.5 billion years old.
They then examined the way the stars move around the center of the cluster to try to calculate the mass of the black hole that should be inside.
This gave a result of about 91,000 solar masses, which makes up about 1.5 percent of the mass of the cluster.
The experts added: “We are in favor of the presence of a single IMBH given the other indications that the B023-G78 is a stripped core, as well as the apparent compactness of the dark component,” they wrote in their paper.
“Higher spatial resolution data would provide improved constraints on the nature of the central dark mass and should have high priority in the coming era of extremely large telescopes.”
The team paper is available on arXiv and will be published by AAS.