What part of the EM spectrum was used in the black hole image? The EHT has published the first image of a black hole.  It is the event horizon of the singularity in M87 against its accretion disk.  I've been through the reports in the popular press but none mention the light wavelengths this was taken at.  Is it an image in visible light, infra-red or longer?
According to the EHT website The observations were done using radio telescopes observing at a wavelength of 1.3mm. Visible light or infrared from the accretion disk would be nearly impossible to detect at such large distances. The radio measurements from all the synchronized telescopes were then combined and converted into an image.