“They’re so cute when they’re babies.”
How many times have you heard someone say that and thought, “What until that grizzly cub grows up.” The only thing cuter than one grizzly cub is a whole bunch of them rolling around and playing. The same goes for baby lions, alligators and probably even sharks. What about baby black holes? Well, you can finally judge baby black hole cuteness for yourself – using the Hubble Space Telescope and the European Space Agency’s Gaia spacecraft, NASA found a group of 60 baby black holes where it was expecting one supermassive black hole to be.
“We found very strong evidence for an invisible mass in the dense core of the globular cluster, but we were surprised to find that this extra mass is not 'point-like' (that would be expected for a solitary massive black hole) but extended to a few percent of the size of the cluster."
In a NASA press release and a new paper published in the journal Astronomy & Astrophysics, Eduardo Vitral of the Paris Institute of Astrophysics (IAP) tells how he and Gary Mamon were studying NGC 6397 – a globular cluster (an extremely dense system of closely packed stars) just 7,800 light-years away. The astronomers were hoping the center of NGC 6397 contained an intermediate-mass black hole (IMBH) – the rarely seen “missing link” of black holes. Instead, they observed a chaos of movement in a space no larger than our own solar system. They concluded that this chaos or “dynamical friction” could be caused by something completely different.
“This invisible component could only be made up of the remnants (white dwarfs, neutron stars, and black holes) of massive stars whose inner regions collapsed under their own gravity once their nuclear fuel was exhausted.”
Using the theory of stellar evolution, they concluded that most of the remnants were not old, dead stars but young, baby black holes playing, rolling around and colliding with each other like a nursery of baby grizzly cubs. That conclusion leads to the next question – will these baby black holes grow up individually, like the grizzly cubs, or will the merge violently into intermediate and supermassive black holes? A black hole collision discovered in 2020 resulted in one of the few intermediate-mass black holes ever detected, so the astronomers are hoping this group might do the same. These collisions/mergers are thought to be a possible cause of gravitational waves, so babysitting the young black holes in NGC 6397 could turn out to be a lucrative, fulltime job.
In the meantime, what’s a good collective noun for a group of baby black holes? A hubble? A gravitas? A collapse? Whatever it is, they’re cute when they’re that age.