Hubble Discovers Missing Link In Evolution Of Earth’s Closest Massive Black Hole

hero hubble black hole evidence
A new image comprising more than 500 images from NASA/ESA Hubble Space Telescope spanning two decades of the innermost region of Omega Centauri provides new evidence for the existence of an intermediate black hole. Astronomers believe elusive intermediate black holes (IMBHs) could hold the ‘missing link’ in black hole evolution.

Black holes have long captivated the minds of scientists and astronomers because of their extreme environments. The vast majority of black holes detected thus far have either been supermassive black holes, or those considered being “lightweight,” or having a mass of less than 100 times that of Earth’s Sun. There have only been a handful of IMBHs detected so far, which makes the possibility of one existing in Omega Centauri, a globular cluster in the constellation of Centaurus, an exciting prospect for helping to unravel the mysteries of how black holes evolve.

Omega Centauri lies 17,700 light-years from Earth. Even though it is quite far from Earth, it can still be viewed in a dark rural area, appearing nearly as large as the full moon. This globular cluster comprises roughly 10 million stars that are gravitationally bound, which led an international group of astronomers to create a vast catalogue of the motions of the stars. While most observations were intended to calibrate Hubble’s instruments, they became an excellent database for the team’s research efforts.

“We discovered seven stars that should not be there,” explained Maximilian Häberle of the Max Planck Institute for Astronomy in Germany, who led the study. “They are moving so fast that they should escape the cluster and never come back. The most likely explanation is that a very massive object is gravitationally pulling on these stars and keeping them close to the center. The only object that can be so massive is a black hole, with a mass at least 8200 times that of our Sun.”

hubble location of IMBH
Location of candidate IMBH in Omega Centauri.

While past studies have hypothesized the presence of an IMBH in Omega Centauri, they proposed the mass could be contributed by a central cluster of stellar-mass black holes. The studies also suggested the lack of fast-moving stars above the needed escape velocity made an IMBH less likely, according to the European Space Agency.

“This discovery is the most direct evidence so far of an IMBH in Omega Centauri,” remarked team lead Nadine Neumayer, also of the Max Planck Institute for Astronomy. “This is exciting because there are only very few other black holes known with a similar mass. The black hole in Omega Centauri may be the best example of an IMBH in our cosmic neighbourhood.”

The international team now hopes to characterize the proposed intermediate-mass black hole, believing it to measure at least 8,200 solar masses. If confirmed to be an IMBH, it would be the only known case of numerous stars being closely bound to a massive black hole.