Until now only two categories of black holes have been found. A supermassive black holes weighting up to billion solar masses to small ones weighting just a few times our Sun. An intermediate category was believed to exist, in which black holes weight between 1000-10000 times and finally evidence have been found of such a black hole. This new type of black hole weights 2,200 solar masses and is found in the 47 Tucanae cluster.
“We want to find intermediate-mass black holes because they are the missing link between stellar-mass and supermassive black holes. They may be the primordial seeds that grew into the monsters we see in the centers of galaxies today,” said lead author Bulent Kiziltan.
The black hole in the 47 Tucanae cluster
The cluster 47 Tucanae is an 12 billion year old one located in the southern constellation of Tucana. It contains thousands of stars in a relatively small space – 120 light years in diameter.
This cluster has been searched for a central black hole but to no avail. They use X-rays to locate a hole feeding on gas in the center, but 47 Tucanae is gas-free which means that black holes in the center could not exist.
In the center of our galaxy, the black hole was found by looking at it influence at individual stars.
However this method is impossible to use because of the massive density of stars in 47 Tucanae.
The researchers used two different methods to find this new black hole. First was the motions of the stars in the cluster. Denser stars tend to sink to the center in such crowded spaces. The IMBH causes the star to slingshot and achieve greater speeds and distances. This gives a faint signal for astronomers to measure.
Using computer models and simulations along with real-world data, it helps them find what causes this gravitational stirring.
The other method used is looking for pulsars in the cluster. They are easy to detect and if a black hole was in the center, they would be thrown farther away if there was no black hole.
The scientists findings gives us evidence of a 2,200 solar masses black hole in the center of 47 Tucanae cluster.
Because such black holes have eluded detection for so long, other may be hiding in dense globular clusters.