There’s some new exciting news for all the space enthusiasts out there! NASA has revealed that its Hubble telescope has uncovered a concentration of small black holes at the heart of the globular cluster NGC 639. Astronomers thought that the globular cluster hosted an intermediate-mass black hole.
“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 per cent of the size of the cluster,” said Eduardo Vitral of the Paris Institute of Astrophysics (IAP) in Paris, France.
The report states that Vitral and Gary Mamon, also of IAP, used the velocities of stars in the cluster to detect the elusive hidden mass and determine the distribution of its total mass, that is the mass in the visible stars, faint stars, and black holes. Researchers conclude that the invisible component can only be made of the remnants of massive stars (white dwarfs, neutron stars, and black holes) given its mass, extent, and location.
These “stellar corpses” progressively sank to the cluster’s centre after gravitational interactions with nearby less massive stars. This game of stellar pinball is called “dynamical friction,”. Under this phenomenon, an exchange of momentum takes place because of which heavier stars are segregated in the cluster’s core and lower-mass stars migrate to the cluster’s periphery.