How was the black hole candidate Cygnus X-1 first discovered?
A) by extremely high spatial resolution radio observations with the VLA radio interferometric array in New Mexico
B) by high-resolution visible-light observations with the Hubble Space Telescope
C) by X-ray measurements with the Uhuru satellite
D) by infrared observations with the IRAS infrared satellite

Question

Quizplus · Accepted Answer

Cygnus X-1 was first discovered as a strong X-ray source by the Uhuru satellite, which was the first satellite launched specifically for the purpose of X-ray astronomy in 1970. The detection of X-rays indicated the presence of extremely high-energy processes, which led to the identification of Cygnus X-1 as a black hole candidate.

How Was the Black Hole Candidate Cygnus X-1 First Discovered