Astronomers have discovered unusual movements of gas clouds near the center of our galaxy, according to a new study, and they may indicate the way to the most elusive types of black holes. For a long time, we weren't even sure if these types of black holes existed.
Researchers tracking gases in the middle of the Milky Way have concluded that clouds orbit an object 10,000 times heavier than the Sun – and yet when they look at where the object should be, there is nothing there.
The most obvious explanation is a quiet black hole that is inactive and therefore does not emit detectable radiation.
We know there are supermassive black holes like the ones that power galaxies. They start at roughly 100,000 solar masses, but they can become almost inconceivably massive.
The class in between – 1,000 to 100,000 solar masses – is called medium-mass black holes. And they raise questions like 'do they exist?' and 'if they don't exist, why?' and 'if they exist, why can't we find them?'
Because black holes do not emit detectable radiation of their own, scientists have to be creative in their quest. Instead of looking for black holes, they look for effects that black holes could have on other objects in nearby space.
Astrophysicist Shunya Takekawa of the National Astronomical Observatory of Japan and his colleagues are studying the movement of high-speed gas clouds in the center of the Milky Way to help answer these questions.
Their paper was accepted by the Astrophysical Journal and is available on the arXiv preprint server.
“One of the three clumps has a ring-like structure with a very steep velocity gradient,” the researchers write in their paper.
'This kinematic structure assumes an orbit around a point object with a mass of ~ 104 solar masses. The lack of stellar counterparts indicates that the point object may be a stationary black hole. '
There was also a strong burst of radiation in 2003 and gradually faded over the decade. The photon distribution suggests that it was an intermediate mass black hole.
The study was accepted by the Astrophysical Journal and is available on arXiv.
