10 Things You Didn’t Know About Black Holes
Stars whose size is 10 or 15 times as massive as the Sun, generally have a fate of becoming black holes. Small stars, however, die as white dwarfs or neutron stars. So how do large stars become black holes? As stars begin to grow old, they gradually expand and they slowly run out of their supply of hydrogen and then helium. This causes contraction of their cores and expansion of the outer layers. The stars start becoming cooler and less bright and they come to a stage which is known as the red giant phase. Now, for a star which is even 3 times or more the mass of the Sun, undergoes detonation (a violent release of energy caused by a chemical or nuclear reaction) in cataclysms known as supernovae. Such kind of explosion results in scattering of most of a star into the space. However, it also leaves behind a cold remnant of the star, which is no longer able to execute any nuclear fusion reaction.
As there is no fusion in the dead remnants of a massive supernova star, there is no creation of any energy which can oppose the inward pull of gravity caused by the star’s own mass. Thus, the star enters a phase where it begins to collapse in upon itself. This is the formation of the black hole, wherein, it starts shrinking to zero volume. So, with volume being zero, density becomes infinite, so much that even light becomes unable to escape its massively strong gravitational pull. As a result of this, even the light of the dead remnants of the star gets trapped in its orbit and this dark star evolves to become what is known as a black hole.
- It has been estimated that there might be black holes of enormous size, which may be existing at the center of our galaxy, ‘The Milky Way’. These holes are assumed to be having the mass of 10 - 100 billion suns. Now, that is something which is ‘HUGE’, in block letters!
- Cygnus X-1 is the black hole that is located about 8000 light years away from our planet Earth. This is the closest black hole to Earth, known to man.
- Although, black holes are associated with the reputation of having the strongest suction force, they do not bear the capability to absorb the whole universe. Anything such as planets, light and other matter, can be pulled into the grasp of black holes, only if they happen to cross what is known as the event horizon. The radius of this event horizon is known as the Schwarzschild radius and at this radius, the escape velocity equals the speed of the light. So, once an object has passed through it, it must travel faster than light in order to escape it. That is the reason why, even light cannot escape the event horizon of a black hole.
- As mentioned earlier, in this part of black holes in space, only the largest of stars are capable to end up as black holes. Only these stars are massive enough to get compressed to the Schwarzschild radius. While, smaller stars end up as white dwarfs or neutron stars.
- There are several black holes which exist in binary star systems. Stars which are neighboring such holes, will keep on shrinking as their mass will continually be pulled by these holes. Gradually, the black holes will go on increasing, until the other stars have vanished.
- As light cannot escape from a black hole, it cannot be directly observed. However, scientists use the presence of matters which swirl around the hole. Such matters are usually gas and dust and they heat up and emit radiation which can be detected.
- Talking about our Sun becoming a black hole, the phenomenon won’t occur. This is because the sun is not massive enough to shrink into a black hole. However, it will end up to become a white dwarf, after several billion years.
- The center of a black hole is void of time and space.
- A giant elliptical galaxy in the constellation Virgo, is assumed to home the largest known black hole. This hole is about 3 billion times the mass of the Sun.
- Larger black holes are known to suck up other smaller ones which are close to their vicinity.
No matter, how many facts people come up with, black holes represent an endless journey in the vast darkness of the space. The concept which lay hidden in the lap of black holes, perhaps, is the most appropriate analogy to the saying ‘sky is the limit!’
In the image: Simulation of gas cloud approaching the black hole at the center of the Milky Way