Black Holes- Sucking Us Back In

Next day, two weeks later, same thing. Got pretty sick there for a while, so it'll take some doing to get caught up, but what can you do.
As I said last time, I'll be continuing on the topic of black holes- Namely, how we detect them. So, how do you detect something that is quite literally invisible? Ordniarily, we see things that reflect or refract light, but black holes, as we discussed, pull light in and don't let it back out. So how do we find them?
There are actually more ways to detect a black hole than you would think. One way was what I discussed previously- quasars. As I mentioned previously, quasars are superheated disks for gas and particulate quickly circling a black hole. Their extreme heat causes them to radiate significantly, so these are actually relatively easy to locate by testing the spectrum given by a radiator, looking for large amounts of x-ray and radio waves. The process in which the quasars is referred to as "accretion," and releases huge amounts of energy relative to the amounts of matter involved- as much as fourty percent of the mass' equivalent in energy is released. Along with quasars are frequently another phenomenon, referred to as "jets." These jets are massive releases of x-rays, which are released in pulses at a right angle to the plane of the quasar. Not much is known about the process by which jets are created, but they are easily observed, and are a good way to find large black holes.

Bear with the video, the quasar and jets show up about halfway through.

Well, finding black holes because they have visible formations around them is well and good, but there are plenty of black holes that don't have quasars. How do we spot those? Well, one solution is to look for gravitational lensing. You remember that, right? Of course you do. It stands to reason, since high-mass objects such as large stars and galaxies can gravitationally lens light around them, black holes, being so massive, can do the same. By searching for instances of gravitational lensing that don't appear to have an object to lens around, you can find black holes.
A third method, and the last I'll discuss, is probably the simplest. This method consists of simply observing stars in an area where it is believed a black hole may exist, and watching the movement of these stars. Their motion can often act as a clue to an invisible large mass, which it is probably orbiting. This is an especially useful method for detecting smaller black holes, those without quasars and jets, and those black holes that are scattered throughout the galaxy instead of occupying its center. This case can also apply in the rare cases where black holes form binaries with stars.

Hopefully this expands your knowledge of black holes, as this is my second post on the topic. Until my next post, happy astronomy!