Black holes are by definition black; they do not emit light directly because nothing can escape them. When we observe them, we look at active black holes. Their strong gravity packed into a tiny space is capable of producing some truly remarkable emissions.
One such example is MAXI J1820+070, a system where a black hole and a star orbit around each other. This black hole, which has a mass of about seven Suns, is stealing material from its companion. As this material gets closer to the black hole it heats up and gets compressed, which makes it start to shine. This light emission flickers and researchers have now described their observations of these very quick changes in the Monthly Notices of the Royal Astronomical Society.
The team used their observations to construct a movie of the flickering light, which includes an animation of the black hole system. The video shows that the material’s glimmering and crackling could easily outshine the star it was stolen from. This was possible thanks to the HiPERCAM and NICER instruments, which detect optical light and X-rays respectively, that captured the changes at over 300 frames per second.
“The movie was made using real data, but slowed down to 1/10th of actual speed to allow the most rapid flares to be discerned by the human eye,” lead author John Paice, a graduate researcher at the University of Southampton, said in a statement. “We can see how the material around the black hole is so bright, it’s outshining the star that it is consuming, and the fastest flickers last only a few milliseconds – that’s the output of a hundred Suns and more being emitted in the blink of an eye!”
The work is more than just a pretty visualization of black hole-related phenomena. It is also very important for understanding how black holes work. The observations show that the X-ray emission from the system dips as the visible light emission increases, and vice-versa. This is not the first detection of this kind, but it has never been seen at this level of detail before.
“The fact that we now see this in three systems strengthens the idea that it is a unifying characteristic of such growing black holes. If true, this must be telling us something fundamental about how plasma flows around black holes operate,” co-author Dr Poshak Gandhi, also at Southampton University, explained. “Our best ideas invoke a deep connection between inspiralling and outflowing bits of the plasma. But these are extreme physical conditions that we cannot replicate in Earth laboratories, and we don’t understand how nature manages this. Such data will be crucial for homing in on the correct theory.”
It is very difficult to study this system as the few known systems like this are so far away from us that they can’t be resolved. MAXI J1820+070 is located 10,000 light-years away.