Why We Can’t Actually See A Black Hole

So if we can’t see black holes themselves, how do we know they are there? And how can we possibly have pictures of them? The answer is that while the black hole itself is invisible, we can observe its effects on the matter around it.

Black holes were predicted to exist as far back as the 1930s, but the definitive proof of their existence arrived in 2015 when scientists observed two black holes colliding and observed gravitational waves created by this merger (via Washington Post). Scientists can see how stars and gas move in distant parts of the universe and infer that there must be a black hole present because of their movements.

Another way to observe black holes is to look for the energy they give off. When any material is drawn toward the event horizon, it rubs up against other material and gets hot, eventually creating a bright glow (via Astronomy.) It is this glow that the images of the two black holes capture.

“Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure,” the Event Horizon Telescope project, the group which produced the two pictures of the black holes, explains. “The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.”