Space

Evidence suggests theoretical 'missing link' black hole exists nearby

A Hubble image of Messier 4, a globular star cluster about 6,000 light-years away that's home to the best evidence so far of an intermediate-mass black hole
ESA/Hubble & NASA
A Hubble image of Messier 4, a globular star cluster about 6,000 light-years away that's home to the best evidence so far of an intermediate-mass black hole
ESA/Hubble & NASA

Black holes come in two distinct types – small and supermassive. A group in the middle has long been hypothesized to exist, and now Hubble has found some strong evidence for one of these intermediate-mass black holes in a nearby star cluster.

Stellar mass black holes are the most common ones, with masses from a few to a few dozen times that of the Sun. Then there’s a gigantic gap between them and the next type of black hole – supermassive monsters with the mass of millions or billions of Suns, which lurk at the center of galaxies.

Astronomers have long suspected that there should be medium-sized black holes in the middle of that range. But strangely, evidence of them is lacking. A few candidates have been spotted here and there, but arguably could still be attributed to other objects and phenomena.

In a new study, scientists claim to have found the best evidence yet for these mysterious missing-link black holes. The team examined 12 years’ worth of Hubble and Gaia data on a globular star cluster called Messier 4, located about 6,000 light-years from Earth, making it the closest cluster to us.

The stars in the cluster seem to be swarming around a large mass in the center, and by watching their motions over that long period of time, they can calculate the mass of that central object. This number came to about 800 solar masses, firmly in the range of an intermediate black hole.

Of course, without directly detecting the object the scientists can’t fully confirm that it is an intermediate black hole. But if it isn’t, the astronomers calculated that it would take about 40 stellar-mass black holes, crammed into a space only one-10th of a light-year wide, to create the same effect. That would be an unstable arrangement, causing them to merge or flick each other out of the cluster.

“While we cannot completely affirm that it is a central point of gravity, we can show that it is very small,” said Eduardo Vitral, lead author of the study. “It’s too tiny for us to be able to explain other than it being a single black hole. Alternatively, there might be a stellar mechanism we simply don’t know about, at least within current physics.”

The research was published in the journal Science.

Source: ESA Hubble

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1 comment
Gene Preston
Galaxies are held together by super massive black holes. This suggests globular clusters are also held together by black holes. What is different about the gravity field from a black hole than a regular star? One possibility is that when the mass collapses the energy of atoms is turned into distributed energy in the gravity field itself, i.e. energy is conserved so the atomic mass plus the gravity energy mass is a constant. If the atomic mass disappears then the gravity field energy is dominant. However the gravity field energy is most likely outside the event horizon whereas the atomic mass is inside the event horizon but has dropped to nearly zero inside the black hole. This loss of atomic mass could explain the reason masses have an attraction force, loss of atomic mass as they get closer to each other. But if the black hole energy is distributed in space it will have a 1/r force component with distance instead of a 1/r^2 Newton force. This 1/r force would explain why stars have nearly constant velocities on the outer edges of galaxies independent of radial distance once out past a distance where the Newton 1/r^2 force is less. The 1/r force can reign in starts that would otherwise exit the globular cluster is why they are stable and exist.