I think this statement isn't quite correct; "This high energy X-radiation lights up the disk, which reflects it, making the disk a source of X-rays"…X-radiation does NOT "light up" the disk, which visually appears black. X radiation is the only radiation that "emanates" from or comes out of the black hole, because of it's unique frequency. The recent ability to focus X-ray radiation has given scientists the ability to "visualize" (but not actually "see") where the black hole is. We can see the stars near the black hole as they "fall in" to it; and this direct vision (not reflection) allows us to quantify the size and density of the black hole. Several photographs have shown this; Search proof of stars falling in to black holes.
More information about text formats