When it comes to size, nearly all the known black holes in the universe fall into two categories: They’re big, or they’re really, really big. Stellar mass black holes weigh up to a few dozen times the mass of our sun, and supermassive black holes can weigh millions or billions times the mass of the sun.
But astronomers have for decades suspected the existence of something in between, intermediate-mass black holes that weigh between 100 and 10,000 suns. Several have put forth observations and measurements of these medium-sized black holes in the last decade, based on telescope data and computer simulations, but their existence has not yet been confirmed with certainty.
Bülent Kiziltan, an astronomer at the Harvard-Smithsonian Center for Astrophysics, says these medium-sized black holes are the “missing link” in the classification of black holes, and could be the ancient seeds that, in some cases, grew into the supermassive black holes that exist at the center of most galaxies.
Kiziltan and his team present their own discovery of an intermediate-mass black hole in a new study published Thursday in the journal Nature. Kiziltan says they have evidence for the existence of a medium-sized black hole at the heart of 47 Tucanae, a 12-billion-year-old ball of of thousands of stars located in the constellation of Tucana, named for the South American bird. The globular cluster is the second-brightest of its kind in the night sky, and can be seen from Earth without a telescope. The black hole, the researchers say, is the mass of about 2,200 suns, the grande in the cosmic version of coffee drinks.