Q&A: Black Holes
If light cannot escape black holes, how can we take pictures of them?
You are correct that light can't escape a
black hole. What we can see in astronomical images is light from material
that is heated up when it gets close to a black hole. This material can
glow very brightly, especially in ultraviolet light and X-rays.
Please see: http://chandra.harvard.edu/xray_sources/blackholes.html for more details.