Researchers from the RIKEN
Nishina Center for Accelerator-Based Science, in collaboration with scientists from Nihon University, Kyoto University, and the University of Tokyo, used an x-ray detector aboard the Suzaku space-based observatory to observe the final moments of matter falling into an enormous object, Cygnus X-1, which is strongly believed to be a black hole.
The group showed that the temperature of gas rose rapidly to a temperature of more than a billion degrees celsius within the last milliseconds as it fell into the object, providing strong evidence that the object is indeed a black hole.
The results were published in Astrophysical Journal (doi:10.1088/2041-8205/767/2/L34).