Yes. Quantum effects at the event horizons of black holes cause them to release Hawking radiation, which is a very weak form of radiation. If large amounts of matter falls into a black hole it emits large mounts of energy in the form of light and x-rays before vanishing within the event horizon.
Black holes emit a form of energy called Hawking radiation, which consists of particles being emitted from the black hole's event horizon. This radiation causes the black hole to slowly lose mass over time.
specifically, "astronomers" that study black holes are called cosmologists.
We cannot see black holes because no light comes from them1. They are so gravitationally massive that even light cannot escape from a black hole, thus the name black hole.1 While there is an emission of matter and energy, called Hawking radiation, that theoretically radiates from the perimiter of a black hole, no energy of any kind (including Hawking radiation) escapes from inside the black hole.
Black holes are believed to emit something called Hawking radiation.
Exothermic reactions release energy.
High-mass stars might become black holes, if the remaining matter (after the supernova explosion) is sufficiently large.
No. Their gravitational pull is simply too great to maintain any kind of atmosphere.
conductive energy
The power or force exerted by black holes is all relative to the size of the black hole. Because black holes have many different sizes, they exert different amounts of forces for each black hole. However, I'm assuming that you are talking about black holes like the super massive black hole located in the center of our galaxy. These kinds of black holes are huge and are so powerful, they can trap light which is traveling 286,000 miles per second. So if you're talking about the big galactic black holes seen in the movies, the answer is the black hole is amazingly powerful and can trap anything that goes past its event horizon (point of no return).
Unfortunately black holes don't evaporate- they are a massive vacuum with a tremendous amount of gravitational force which can theoretically disassemble matter which then travels through the hole, and is reassembled (not necessarily in it's original form) at the other end of a black hole commonly called a white hole.
Calories Q
A black hole has an escape velocity of the speed of light, at least theoretically. Oddly, though, each galaxy has a black hole and we can detect them because they throw off massive amounts of energy. If the escape velocity is greater than the speed of light, then no light or energy of any kind should escape. So black holes are not quite the perfect consumers of everything.