The Mystery of Black Holes

With so much unknown about the universe that we live in, it's hard to know which theories are true and which are just pure speculation, but black holes seem to be the real deal. I saw a documentary that really got me started on black holes and their origins and it fascinates me how little we really know about them.

Just a few days ago, the existence a black hole 400 times the mass of our sun in the Cigar Universe has been confirmed by researchers from the University of Maryland [source]. Not many black holes have been discovered, especially of intermediate size like this one, so this is an important scientific discovery!

But how is a black hole created?

When the biggest stars die, they explode into supernovas, like the image below.

Once a star expands to a certain extent, it has too much mass to keep from collapsing into it's own gravity. The mass becomes so great that not even light can escape the gravitational pull of the collapsed star. This is what we consider to be a black hole.




The interesting thing about this newly discovered black hole is that we haven't really come across a black hole this size before. Most of the known black holes in the universe are 10-25 times the mass of our sun and are usually only discovered when another star begins orbiting them, making it look like the star is orbiting nothing, or when light from another star is bent while getting sucked into the gravitational pull of the black hole. The other types of known black holes are called "supermassive" black holes [source]. These are billions of times the mass of the sun and are hypothesized to be the centre of every galaxy. Many scientists believe that the existence of galaxies is because of the gravitational pull of these massive black holes pulled the galaxies, as we know them, together.

Seen to the right is an animation representing gravitational lensing, which is essentially when light is bent by the gravitational pull of an object in space, in this case a black hole [source]. In the animation, there is a galaxy behind the black hole and the light is bent and distorted by the extreme gravity and mass of it, creating a distorted sort of double-image.





There is still some doubt regarding the existence of black holes and it has become sort of a controversial subject in the scientific community. Supposedly, at a certain distance away from a black hole, the gravity is so much and space-time is so warped there is no possibility for anything - even light - to escape. This point is known as the 'event horizon' of that black hole. However, the reputable scientist Stephen Hawking has recently suggested that this might not be the case. Hawkings suggests that it is against fundamental laws of physics. Thermodynamics' second law states that the amount of disorder [entropy] in a system can never be destroyed, which basically boils down to the fact that information can never be destroyed [source]. The common theory about black holes had been that once something crosses the event horizon, it won't ever come out again, and Hawkings suggests a reformulated hypothesis. He is proposing the existence of an 'apparent horizon' which would only contain the matter temporarily before releasing them, although it would be in a more distorted form [source] .

Hawkings does admit that his new theory far from explains the true mystery of black holes, as it doesn't align perfectly with all laws of physics, but it's a step in the right direction, and hopefully we'll be making more leaps and bounds in the near future.

The first theory about the possibility of black holes was over two hundred years ago, and since then we've learned so much, but we're still so clueless about this mysterious universe that we live in. Will we ever figure it all out?