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Astrophysicist Dan Wilkins from Stanford University noticed a pattern in X-rays being emitted into the universe by the black hole supermassive at the centre of a galaxy 800,000,000 light-years away. The bright flares of Xrays were exciting, but not unusual. However, Dan Wilkins noticed something surprising: Additional flashes of Xrays, smaller and later than the bright ones.
These luminous echoes could be consistent with Xrays reflected from the black hole, according to theory. However, even a basic understanding black holes will tell you that it is a strange location for light to come.
Wilkins is a researcher at the Kavli Institute for Particle Astrophysics at Stanford and SLAC National Accelerator Laboratory. He said, "Any light that goes in that black hole doesn’t come out, so it shouldn’t be possible to see anything behind the black hole." This observation is possible due to another peculiar characteristic of the black holes. Wilkins explained that the black hole is warping space and bending light, twisting magnetic fields and bending light around itself.
This strange discovery was made in Nature's July 28th paper. It is the first direct observation that light passes behind a blackhole. It was predicted by Einstein's theory general relativity, but has never been confirmed.
"Fifty years ago when astrophysicists began speculating on how the magnetic field might behave near a black hole," Roger Blandford, a coauthor of the paper, said that they didn't know that we would one day have the tools to observe it directly and see Einstein’s general theory of relativity in practice. He is also the Luke Blossom Professor at Stanford and SLAC professor of physics and particle physics.
How to spot a black hole
This research was started to discover more about the mysterious corona, a feature that black holes have. The supermassive black holes are the most powerful and continuous sources of light. As it falls into them, material forms a corona around them. This light, which is X-ray radiation, can be used to analyze and map a black hole.
According to the leading theory, a corona can be described as gas sliding into a black hole. This superheats it to millions of degrees. At that temperature electrons separate themselves from atoms and create a magnetized plasma. The magnetic field is caught up in the spin of the black holes and creates a magnetized plasma. This situation is so similar to what happens around the Sun that it was given the name "corona."
Wilkins stated that the magnetic field being tied up and then snapping near to the black hole heats all around it and produces high-energy electrons, which then go on producing the Xrays.
Wilkins inspected the source of the flares closer and saw several smaller flashes. These flashes, according to the researchers, were the same Xray flares, but they were reflected from the backside of the diska first look at the far side a black hole.
Wilkins stated, "I have been making theoretical predictions about how these echoes will appear to us for quite a while," "I had seen them in my theory, so when I saw them in telescope observations, I was able to figure out the connection."
It is still necessary to observe more coronas in order to understand and characterize them. The European Space Agency's advanced telescope for high-ENergy Astrophysics, Athena, will play a part in that future. Wilkins, a member the Stanford Physics Lab and of particle physics at SLAC is working on the Wide Field Imager detector.
Wilkins stated that the telescope has a larger mirror than any X-ray telescope, which will allow for higher resolution views in shorter observation times. These new observatories will make the image we're getting from data much more clear.
This research was co-authored by Saint Mary's University (Canada), The Netherlands Institute for Space Research, (SRON), University of Amsterdam, and The Pennsylvania State University.
Learn more about how the universe mirrors near black holes
More information: Light bending, X-ray reflections and X ray echoes are generated by a supermassive dark hole. Nature (2021). www.nature.com/articles/s41586-021-03667-0 Journal information: Nature Light bending and X-ray echoes from behind a supermassive black hole,(2021). DOI: 10.1038/s41586-021-03667-0