Black holes are undoubtedly one of the most stupefying astronomical phenomena till date. For over a century numerous astrophysicists have been intrigued by the unconventional science behind black holes and have willingly dedicated their research to understand it.
The origin story
Like most discoveries in astronomy, the idea of black holes was instigated when the inquisitive eyes of a scientist meets a mystifying problem. In this case the problem was mathematical in nature, and oddly solving equations on a piece of paper seemed to make scientists interpret cosmic phenomena occurring light years away !
So just to brush the details, In 1915, Einstein formulated 10 equations called “Field equations” in his general theory of relativity. These equations described the geometry of spacetime & the distribution of matter in it. Moreover, these equations were non-linear in nature, which meant that it was impossible to find an “absolute” solution for it. Naturally any attempt at solving it involved mind-boggling math !
But in 1916,a physicist named Karl Schwarzschild successfully solved the field equations by making an important assumption. He assumed that if we could squeeze space-time into a minuscule point called Singularity the equations can be solved. In simpler terms his approach described the gravitational fields of a spherical point mass. This assumption is where the idea of black hole was born.
What's even more interesting is that all these discoveries came amidst the raging World War 1. This was unquestionably very commendable because Karl Schwarzchild at that time was serving the German army on the Russian front.
“As you see, the war treated me kindly enough, in spite of the heavy gunfire, to allow me to get away from it all and take this walk in the land of your ideas.”
“ I have read your paper with the utmost interest. I had not expected that one could formulate the exact solution of the problem in such a simple way. I liked very much your mathematical treatment of the subject “
So now what is black hole?
Fundamentally it’s a point in space which is exceedingly dense. The gravitational field around this point is so high that if any object even dares to come close it ends up being “spaghettified”
(There is an actual scientific process in astrophysics called “spaghettification” or “noodle effect” which describes the shrinkage & extrusion of a body in space caused by extreme forces)
How are black holes formed in the first place ?
The death of a star is responsible for the formation of a black hole. Firstly, stars have a stellar core with a very high gravitational field. When a star is “Alive” this gravitational force is balanced by nuclear fusion reactions, but when a star dies all the matter is dispelled into space in the form of a supernova.
But surprisingly the Stellar core remains behind. Due to the absence of any nuclear fusion to counteract the gravitational pull the stellar core ends up collapsing in itself. This leads to an irrepressible chain reaction which exponentially increases in intensity and leads to the formation of a black hole. This type of black hole is called a stellar black hole.
How can we find a Black hole?
The gravitational pull of black holes are extremely strong that they tend to swallow light as well ! Hence, it's impossible to spot them directly. The only way of detecting one is by studying its gravitational effects on surrounding objects. Celestial bodies and stars show erratic movements in the presence of black holes and this is how “Sagittarius A*”a supermassive black hole in the center of the Milky Way galaxy was discovered.
However, it was also theorized that black hole images can be captured by the silhouettes they cast against their glowing surroundings. Employing this idea the Even horizon telescope network was concepted. These telescopes utilized a technique called Very Long Baseline Interferometry (VLBI) to capture the groundbreaking image of a black hole on April 10th 2019.
What lies ahead …
So far there are 4 types of black holes namely stellar, intermediate, supermassive & miniature black holes lurking in space. Most of these types have only been described theoretically. Furthermore, there is also the idea of binary black hole systems which are predominantly found on tightly clustered galaxies. We still do not have any evidence as to why they behave in such a manner or where we can find them.
One thing we can infer with certainty is that over the past few years the research in this field has been accelerating. This is done in the hope of finding any significant leads to demystify the black hole.
At this pace, in the next few decades we could probably discover something as phenomenal as time travel or just end up messing physics to a whole new level, only time will tell …
For those space geeks who are curious about the significance of Dark matter and Dark energy, check this article out !