Stellar black holes formed after a massive star gravitational collapses have masses ranging from between 5 and 100 times that of the Sun. Supermassive black holes (SMBH) that lurk at the centre of galaxies, on the other hand, can theoretical have masses of up to 50 billion times that of our sun, with the one at the centre of the Milky Way having around 4.5 million solar masses.
Galaxy collisions, which are quite common in space, should therefore produce supermassive black hole pairs that are growing rapidly as they disrupt each others mutual gravitational forces and internal structure. As Sara Ellison from the University of Victoria explains:
“These internal disruptions perturb the orbits of the galaxy’s stars and can cause the gas that resides in the interstellar medium to get funnelled towards the galactic centre. This process provides a ready supply of fuel to the supermassive black hole that is located at the galaxy’s centre – it’s like turning on the tap and watching the material go down the plug hole!”
Until recently, however, fewer than ten pairs of rapidly growing black holes had been discovered, but now astronomers using optical data collected from the Sloan Digital Sky Survey (SDSS), NASA’s Chandra X-ray Observatory, and the Wide-Field Infrared Sky Explorer Survey (WISE) have unveiled a further cache of five such pairs. The researchers behind the discovery published their findings in the Astrophysics Journal, and have hailed the combining of infrared and X-ray data as an efficient method of making similar detections going forward.
This has implications for the study of a whole field of astronomical phenomena, not least gravitational waves, which should be produced as the supermassive black holes at the centre of colliding galaxies draw ever closer. Commenting on the development, astrophysicist from Shobita Satyapal from George Mason University, stated:
“It is important to understand how common supermassive black hole pairs are, to help in predicting the signals for gravitational wave observatories. With experiments already in place and future ones coming online, this is an exciting time to be researching merging black holes. We are in the early stages of a new era in exploring the universe.”