All you need is an 8-inch telescope and some patience.
Black holes are one of those things in astronomy that we all know exist but that few people have seen. They bring with them a sense of awe and wonder. Scientists still don’t fully understand them, but they do create distortions in space that affect our galaxy and beyond.
Up until now, astronomers needed high-spec X-ray or gamma-ray telescopes in order to observe black holes. However, an international research team out of the University of Kyoto reports that it is possible to observe them by looking for visible, flickering light from gasses around the holes during outbursts.
"We now know that we can make observations based on optical rays — visible light, in other words — and that black holes can be observed without high-spec X-ray or gamma-ray telescopes," explains lead author Mariko Kimura, a master's student at Kyoto University. The team published their results in Nature and explained that optical rays are enough to spot a black hole.
The traditional method for observing a black hole is to wait several decades for a black hole binary to undergo an “outburst” where an extremely large amount of energy is produced from substances falling into the black hole. Black holes are typically surrounded by what is know as an “accretion disk,” a ring of gas from nearby stars that forms a spiral pattern as it is drawn towards the black hole. What astronomers observe are the X-rays generated in the innermost parts of these accretion disks. There, temperatures reach over 10 million degrees Kelvin.
On June 15, 2015, V404 Cygni, a 26-year dormant black hole binary, came to life with an outburst. The Kyoto University team’s astronomers were able to collect huge amounts of data and determined that the optical fluctuation patterns correlated with the X-ray ones.
Kyoto astronomers and their collaborators at the National Space Agency JAXA, National Laboratory RIKEN, and Hiroshima University showed that the X-rays coming from the inner regions of the black hole’s accretion disk irradiate outwards, heat the outer regions, and cause it to emit visible rays.
"Stars can only be observed after dark, and there are only so many hours each night, but by making observations from different locations around the globe we're able to take more comprehensive data," says co-author Daisaku Nogami. "We're very pleased that our international observation network was able to come together to document this rare event."
So if you’ve got a decent telescope, add black holes to the list of nightly things you search for. They’ll make you forget all about Saturn’s rings and the moon’s craters!
Based on information provided by Kyoto University.