You know what they say that you have to be careful what you wish for. Black holes easily qualify as one of the most dangerous types of objects in the Universe, but our reality can become even scarier than that. Scientists were fascinated by the stellar cluster known as NGC 6397, which’s located about 7,800 light-years away. While hoping to detect a supermassive black hole at the cluster’s centre, researchers were astonished to find a swarm of smaller black holes.
The New York Times writes about the unexpected discovery made by Eduardo Vitral and Gary A. Mamon from the Paris Institute of Astrophysics, and there’s even more incredible data on the small black holes found. The tiny pieces of absolute darkness have all crammed inside a space almost the same size as our Solar System.
The Hubble space telescope is still great
Hubble is slowly and surely approaching its demise, as it will be replaced by the next-generation James Webb telescope in October 2021. But the current telescope still proves itself very useful, and the scientists used data from it and from the European Space Agency’s Gaia spacecraft to discover the small black holes from the core of NGC 6397.
The scientists’ work also suggests colliding black holes could be a source of gravitational waves detected by LIGO and Virgo antennas. But although there was no giant black hole in the cluster as scientists were expecting, we have reasons to believe that it can happen otherwise someday. Gary A. Mamon supports an idea known as ‘dynamical friction’, meaning gravitational interactions of the small black holes from NGC 6397 with less massive stars, leading to speed loss and the shifting towards the cluster’s centre:
This may bring the black holes to the center in a few million years, where they merge into an intermediate-mass black hole.
Eduardo Vitral emphasizes the importance of the discovery:
Our discovery of this invisible concentration in a core-collapse globular cluster is surely something that makes us wonder about many ideas of intermediate-mass black hole formation!
The new findings were reported in Astronomy and Astrophysics.