I don't think it's really necessary to say, but when people think about space, especially for those of us who aren't exactly experts in the field, things like supernovas, black holes, etc. seem particularly interesting. The primary topic I'd like to talk about right now is black holes - something that, due to its nature, isn't particularly easy to study. You can't see the black hole itself, nor are we exactly capable of approaching one to study in person. Although the idea of an object of sufficient mass and density have a powerful enough gravitational field to affect light itself was first proposed in the 18th century by the geologist John Michell, the idea of the black hole did not gain much ground until Albert Einstein developed his theories on general relativity in 1915. The combined work of Karl Schwarzchild and independently, Johannes Droste, gave way to the Schwarzchild Radius, the radius at which an objects compressed mass would create a gravitational field from which the escape speed is equal to the speed of light. As a result, black holes are in essence, objects which have been compressed beyond the Schwarzchild Radius. While it is impossible to observe an object once it falls into the black hole, from the interaction with matter around it, it is possible to observe mass ,charge, and angular momentum. The information-loss associated with objects falling into a black hole is something that can be described by both quantum mechanics and general relativity, and is known as the Black-hole information paradox (maybe I'll talk about that later...). The aspects of a black hole can be described in 4 pieces, the event horizon, singularity, photon sphere, and ergosphere. The event horizon is so name due to the fact that at the point of the event horizon is essentially the point of no return, as any information that passes through the point is no longer able to escape the gravitational pull of the black hole. Usually, this is observed as the glowing ring around a very dark region of space that marks a black hole. The singularity is considered to be the very center of a black hole where, theoretically, according to general relativity, the entirety of the black holes mass is contained in zero volume. The implication of this is a single point of infinite gravitational field and spacetime curvature. A photon sphere is the point at a certain radius from the center of a black hole where photons moving tangent to the black hole are permanently trapped in a circular orbit. While it is possible for light to escape from within the photon sphere, due to the exact properties of a black hole, the light escaping and observed must come from an object trapped within the photon sphere but outside the event horizon. According to general relativity, due to the gravitational field of a black hole, a certain region of spacetime right outside the radius of a black hole will be permanently "dragged" along. This region of perpetual motion is what is known as the ergosphere - a region surrounding the event horizon from which an escaping object can emerge with greater energy than it entered, taking with it some of the energy of the black hole. At this point, it would be pretty wordy to get into more detail with black holes, so I may save this for another post... but in a nutshell, black holes form through gravitational collapse, typically when stars run out of fuel to sustain its size. Here's a pretty picture to distract people again.