Astronomers have discovered a huge, rare black hole lurking in the star cluster Omega Centauri, thanks to "smoking gun" evidence provided by fast-moving stars.
Long-Sought Mid-Size Black Hole
Astronomers have initially found the closest massive black hole to Earth, said to be a cosmic titan "frozen in time," using the Hubble Space Telescope. The findings are reported in a paper titled "Fast-moving stars around an intermediate-mass black hole in ω Centauri."
The newly discovered black hole lies within the globular cluster Omega Centauri, located about 18,000 light-years away from Earth, with a foreseen mass of 20,000 times that of our own Sun. It would then be classified as the best candidate for intermediate-mass black holes formed within the early phases of galaxy evolution.
Omega Centauri is an enormous collection of some 10 million stars that appear as a smudge in the night sky from southern latitudes. In a small telescope, it looks just like any other globular cluster: too dense toward the center to distinguish individual stars.
For decades, astronomers have suspected that a black hole resides at the center of Omega Centauri.
A team of researchers led by Maximilian Häberle scoured for stars zipping by, which should exist next to such concentrated masses as black holes. Then, they compared them with theoretical models of what the possible movement of stars would look like if a black hole actually existed.
The discovery was made after scientists used images taken from 20 years of study over a million stars in the Omega Centauri cluster. This is a rare uncovering of an intermediate-sized black hole-something that might have resulted from a smaller galaxy being devoured by our own Milky Way.
The Missing Link
Astronomers say the newly discovered black hole could represent a missing link between the smaller stellar black and much larger supermassive black holes. This cosmic void appears to be stuck in an intermediate stage of its evolution and is considerably less massive compared with usual black holes residing at the centers of galaxies.
Stellar black holes form from the remains of massive stars that explode in a supernova. In most instances, they have masses 5-150 times that of our Sun.
On the other hand, supermassive black holes are much larger, with masses ranging from hundreds of thousands to billions of solar masses. They are seated at the centers of most galaxies, including our own Milky Way.
It turns out that this newly found black hole in the heart of Omega Centauri lies somewhere between the stellar and supermassive galaxies. It beats the Milky Way's central supermassive black hole Sagittarius A*, being at least 27,000 light years away from Earth.
This might have happened because Omega Centauri was once a young galaxy's core; the black hole was just that of a teenage galactic core, which created a supermassive black hole over time. Its growth may have gotten stunted once the Milky Way ate the smaller galaxy, leaving it "frozen in time."
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