A black hole is a zone of spacetime which has gravitational acceleration so strong that nothing can escape from it: particles, radiation (light) are all swallowed never to be seen again.
Sagittarius A*, the central black hole of the Milky Way is regularly quite subdued, recorded activity levels being low over the course of the past years. However, in May, scientists from all around the world detected an “unprecedented” bright flash coming from the black hole.
It’s normal for supermassive black holes to feature slight brightness fluctuations, but when the black hole (which is four million times the mass of the Sun) had gotten 75 times brighter than usual, scientists were stunned. Tuan Do from UCLA declared: I was pretty surprised at first and then very excited”.
Do also stated: “The black hole was so bright I at first mistook it for the star S0-2, because I had never seen Sagittarius A* that bright. Over the next few frames, though, it was clear the source was variable and had to be the black hole. I knew almost right away there was probably something interesting going on with the black hole.”
Scientists’ studies revealed that the flash happened over a two hour time span. They believe that the change in activity at the supermassive black hole provoked the increase in brightness.
Another speculated cause is a possible change of accretion state – the way the black hole is drawing matter inwards.
It is known that black holes themselves do not emit radiation detectable by Earth observers, but objects and materials close to them do, and perhaps changes to the black hole can excite matter nearby, allowing scientists to detect changes taking place.