Black Holes

By: Anushka Durg


Black holes have been objects of theoretical study for many years. But, one finds it very hard to give an exact definition for black holes. The problem is black holes are defined differently in different fields. In astrophysics, it is the last stage of a star. In general relativity, it an object that curves space-time maximum. Let's look at some interesting aspects of these mysterious objects.


Generally, Horizons are characterized by their horizons and singularity. In astrophysics, horizons are a boundary beyond which events cannot affect an observer on the opposite side of it. An event horizon is most commonly associated with black holes, where gravitational forces are so strong that light cannot escape. In theoretical

Physics, one notices other definitions of horizons, namely the Isolated and Dynamical horizon. These horizons are of greater importance compared to the local event horizon As Isolated horizons, and Dynamical horizons are local. Local means one needs to know the structure of space-time around such a horizon to locate them. However, an event horizon is non-local. Non-locality means that one needs to understand the entire structure of space-time.

Singularity refers to a location in space-time where the gravitational field of a celestial body is predicted to become infinity.


There are three parameters that we need to consider when we talk about the Blackhole: its charge, mass, and angular momentum.


Physicists use the above parameters to understand the black hole’s properties and behavior. Based on the above parameters, we can roughly categorize black holes into four types: The Schwarzschild( nonrotating and uncharged), Reissner–Nordström(charged and nonrotating ), Kerr(uncharged and rotating), and Kerr–Newman( charged and rotating).

Although we can still not precisely define a black hole, these objects are crucial to understanding the secrets of our universe.


Sources

https://arxiv.org/pdf/1808.01507.pdf

https://en.m.wikipedia.org/wiki/Schwarzschild_metric

arXiv:gr-qc/0407042

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