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Thousands of Undiscovered Black Holes Found

A recently released study conducted by the University of Surrey, supported by the European Research Council, shows that there could be hundreds of black holes in a globular cluster, rewriting theories of how black holes are formed.

Hubble Telescope observation of the central region of globular cluster NGC6101

Hubble Telescope observation of the central region of globular cluster NGC6101

Miklos Peuten, of the University of Surrey and lead author, explains,

Due to their nature, black holes are impossible to see with a telescope, because no photons can escape. In order to find them we look for their gravitational effect on their surroundings. Using observations and simulations we are able to spot the distinctive clues to their whereabouts and therefore effectively “see” the unseeable.

Using advanced computer simulations, the researchers were able to map a globular cluster named NGC6101. A globular cluster is a spherical gathering of stars, which orbit around a galactic center. This particular cluster was selected for further study because of its recently-discovered, distinctive composition, showing that it is more unique than other clusters. Cluster NGC6101 is younger than the ages of individual stars and appears inflated, with a core under-populated by observable stars.

The NGC6101 globular star cluster is located about 47,600 light-years from the Sun in the constellation Apus. It is 36,500 light-years from the galactic center. The cluster was discovered on June 1, 1826 by Scottish astronomer James Dunlop.

Though astrophysicists first found black holes in globular clusters in 2013, this new study reveals that NGC6101 contains hundreds of black holes, until now thought impossible. Previously, it was thought that these black holes would almost be expelled from the parent cluster due to the effects of a supernova explosion during the death of a star. However, the black holes are a few times larger than the Sun and form in the gravitational collapse of massive dying stars.

Professor Mark Gieles of the University of Surrey and co-author says,

Our work is intended to help answer fundamental questions related to dynamics of stars and black holes and the recently observed gravitational waves. These are emitted when two black holes merge, the cores of some globular clusters may be where black hole mergers take place.

These systems may be the cradle of gravitational wave emission – “ripples in the fabric of space time.”

Using computer simulation, the researchers recreated every individual star and black hole in the cluster and their behavior, The simulation showed how NGC6101 evolved over the whole lifetime of thirteen billion years. It revealed the effects of large numbers of black holes on the visible stars.

Miklos Peuten of the University of Surrey

Miklos Peuten of the University of Surrey

Peuten sums up,

This research is exciting as we were able to theoretically observe the spectacle of an entire population of black holes using computer simulations. The results show that globular clusters like NGC6101, which were always considered boring, are in fact the most interesting ones, possibly each harboring hundreds of black holes. This will help us to find more black holes in other globular clusters in the Universe.