SALT LAKE CITY — In a galaxy that spans several light-years and is more than 13 billion years old, it makes sense that major astronomical discoveries come few and far between — which is not entirely logical.
Omega Centauri, a global cluster of millions of stars, lies in the Milky Way galaxy—so dense toward the center that it becomes impossible to distinguish individual stars—and can only be seen as a tiny dot in the night sky from southern latitudes.
But within this cluster is something that astronomers have sought and debated for nearly a decade, something a new study led by researchers from the University of Utah and the MacPlanck Institute for Astronomy has revealed: Omega Centauri is home to a central black hole.
“This is a once-in-a-career discovery,” said Anil Seth, associate professor of astronomy at the University of Utah and co-principal investigator of the study. “I’ve been excited about it for nine straight months. Every time I think about it, I have trouble sleeping.”
“On Bigfoot level”
the StadyBlack holes come in a variety of mass ranges, a study published in the journal Nature on Wednesday found.
Common black holes include stellar black holes, which have masses ranging from one solar mass to a few tens of solar masses, and supermassive black holes, which have masses up to billions of solar masses.
Among the most difficult objects that cannot be detected with certainty – so far – are intermediate-mass black holes, which the research team discovered.
“These intermediate-mass black holes are a bit like the black holes that live in the Bigfoot constellation,” said Matthew Whittaker, a University of Utah undergraduate and co-author of the study. “Discovering them is like finding the first evidence of a black hole — people are going to freak out.”
needle in a haystack
Omega Centauri appears to be the heart of a small, detached galaxy that stopped evolving when it was swallowed by the Milky Way, according to the paper. The current state of galaxy evolution suggests that these early galaxies would have had intermediate-sized central black holes that would have grown larger over time.
But how do you start looking for one?
Seth and Nadine Neumeier, group leader at the Max Planck Institute and principal investigator of the study, first began investigating how to better understand Omega Centauri’s formation history in 2019.
They realized that if they could find fast-moving stars around its center, they would finally be able to settle questions surrounding the cluster’s central black hole by measuring the black hole’s mass.
This search for stars fell into the hands of Maximilian Haberl, a doctoral student at the Max Planck Institute. Haberl led the development of a huge catalogue of star motions in the Omega Centauri cluster, measuring the velocities of 1.4 million stars by studying more than 500 Hubble images of the cluster.
The challenge here was that most of the images Haberle had at his disposal were intended to calibrate Hubble’s instruments, not to aid groundbreaking scientific discoveries.
However, with over 500 images, this unintended dataset served its purpose.
“Searching for high-velocity stars and documenting their motion was like looking for a needle in a haystack,” Haberli said. In the end, Haberli not only had the most complete catalog of stellar motions in Omega Centauri to date, but he also found seven needles in his archival haystack—seven fast-moving stars in a small region at the center of Omega Centauri.
Discovery
But the work did not end with the discovery of these seven stars. Thanks to the presence of seven stars, each with different speeds and directions of motion, the researchers were able to separate the different effects and determine the presence of a central mass in Omega Centauri, with a mass of at least 8,200 Suns.
Furthermore, the images do not indicate any visible objects at the location of that central mass as would be expected for a black hole.
Further analysis yielded more good news for the team. As the paper explains, the lone high-velocity star in the image may not belong to Omega Centauri. It could be an outside star that is passing behind or in front of the center of Omega Centauri by chance. On the other hand, the observations of seven such stars cannot be a coincidence and leave no room for explanations other than a black hole.
He died.
move forward
The team now plans to build on their massive findings by further examining the center of Omega Centauri. Seth is leading a project that has received approval to use the James Webb Space Telescope to measure the high-speed motion of stars toward or away from Earth.
like Tools of the future It can be put forward Locating stars With greater precision than Hubble, the goal is to determine how stars accelerate and how their orbits bend—although that project will fall into the hands of future generations of researchers.
However, this discovery strengthens the case for Omega Centauri as the core region of what was once a galaxy that was swallowed up by the Milky Way billions of years ago.
For those interested in hearing directly from the researchers, Seth will present the team’s findings on August 8 at 7 p.m. at the Clarke Planetarium IMAX Theater in Salt Lake City. In the meantime, the full study can be found here Connected.
“I think extraordinary claims require extraordinary evidence. And this is really extraordinary evidence,” Seth said.
“Infuriatingly humble alcohol fanatic. Unapologetic beer practitioner. Analyst.”