Scientists say elusive object found just 18,000 light years from Earth at the center of Omega Centauri
Astronomers have found compelling evidence for a long-sought intermediate-mass black hole lurking at the heart of Omega Centauri, the largest and brightest globular cluster visible from Earth. This cosmic behemoth, weighing in at over 20,000 times the mass of our Sun, bridges the gap between stellar-mass black holes formed from collapsed stars and the supermassive monsters found in galactic centers.
The key to uncovering this elusive object? A group of stars behaving in a most peculiar way.
Using over two decades of ultra-precise observations from the Hubble Space Telescope, researchers detected seven stars near the cluster’s core zipping along at breakneck speeds – far faster than should be possible if only the combined gravity of the cluster’s normal stars was at play. These stellar speedsters are the smoking gun pointing to a massive, invisible object exerting its gravitational influence.
The discovery is akin to finding a group of cars racing around an empty lot at 200 mph. You’d immediately suspect there must be some kind of racetrack or hidden structure guiding their motion. In this case, that hidden structure is the gravity of an intermediate-mass black hole (IMBH). Study authors consider IMBHs to be the “missing link” in black hole formation.
‘Needle in a haystack’
Omega Centauri has long been a tempting target in the search for these middleweight black holes. As the remnant core of a dwarf galaxy consumed by the Milky Way long ago, it seemed a prime candidate to host such an object. Previous studies hinted at its presence, but debates raged over alternative explanations and the lack of definitively fast-moving stars – until now.
“Previous studies had prompted critical questions of ‘So where are the high-speed stars?’ We now have an answer to that and the confirmation that Omega Centauri contains an intermediate-mass black hole,” explains Nadine Neumayer, a group leader at the Max Planck Institute for Astronomy, in a statement. “At a distance of about 18,000 light-years, this is the closest known example of a massive black hole.”