Detecting Black Holes

Black Holes are well, black. They do not reflect or emit light like other objects do, which makes them harder to detect. 

But a thing black holes can do pretty efficiently is to influence their surroundings. We can detect planets orbiting around something invisible, something that has been creating a lot of gravitational pull in the interstellar regions. For example, the centre of the milky way is a dark spot that is surrounded by millions of orbiting stars, clouds and planets, which is how we know a supermassive black hole lies there.

Because of this gravitational pull, anything that comes near the black hole is swept to its "Accretion Disk".  Accretion means the collection of surrounding material through gravitational attraction. This disk is the glowing part that surrounds a black hole, like the orange ring you saw in Interstellar. Some of the matter that falls in the disk releases energy in the process, such as X-Rays which we can detect on Earth. 

That's it about black hole detection, enjoy your life.