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What Are Black Holes ?
Death by Black Hole by Neil deGrasse Tyson
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Black holes are without any doubt the strangest of objects in this cosmos that we live in. In 1915 Einstein came up with his General Theory of Relativity wherein it was theorised that gravity can bend light .Moving forward logically the theory suggest that if mass were packed together to a point with zero volume it will warp spacetime to the point where even light cannot escape thus forming a black hole. Einstein himself could not bring himself to believe that such an object could exist so he dismissed it as impossibility even though the mathematics of his equations pointed towards the fact that indeed they are very real. The term Black Hole was first coined by John Wheeler in a lecture of his in 1967.
A Brief History of Time
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How do Black Holes Form?
How do these stellar monstrosities come into being this is a question which has plagued scientist for a long time but years of research has shone some light on the topic .Black Holes form at the end of the life of a massive star when all its fuel is consumed. The star no longer has enough energy to keep it self from collapsing under its own weight. That is the energy released from the fusion reactions in the star can no longer withstand the strength of the gravitational forces. When a star reaches this stage in its life it collapses inwards into itself and the result is a massive explosion called a supernova. Supernovas are the most violent events that take place in our present day cosmos energies released in this event are exceeded only by the big bang itself. After this violent paroxysm a stellar remnant is left but without the full power of nuclear reactions taking place within it continues to collapses further inward into itself as it cannot support its own mass. At this point something strange happens all the mass of what once was a star is crushed into a space of zero volume and infinite density. This strange new phenomenon is called a singularity a point of infinite density and no volume. Scientist have theorised that if a star has more than 3.2 solar masses there is nothing stopping it from collapsing into a black hole. One solar mass is equivalent to the mass of the sun.
Black Holes have a mathematical border called an event horizon it is a spherical surface that marks the point of no return. Once you cross the event horizon you have no hope because you will be drawn closer and closer towards the singularity that sits within. An object falling into the singularity will eventually be absorbed into it. Another name for the event horizon is the Schwarzschild radius .If the sun were to be squeezed to form a black hole its Schwarzschild radius would be 3 km its current radius is 700000 km. The more massive a black hole is the more space it will take up.
How do we detect a Black Hole?
The event horizon is point if crossed gravitational attraction becomes so great there is no escape. Even light cannot escape beyond the event horizon. This means we cannot see black holes, so how do we know they are there. There are certain characteristics that manifest themselves when matter falls into or comes within proximity to a black hole. Stellar gases and materials falling into a black hole gain massive amounts of energy due to the pressures they are being subject to. At these energy levels the matter starts to emit x-rays that we can detect here on earth. The presence of black holes can also be detected in the orbits of stellar objects like stars.
Super Massive Black Holes
Black Holes are found at the centre of all galaxies so obvious they have a crucial role to play in the formation of the very same and ultimately the creation of life itself. Minor black holes are also scattered throughout galaxies .Right at the centre of the Milky Way Galaxy there is a super massive black hole. It is around 26,000 light years away from the Earth and has a weight of 4 million solar masses .It is a 15 million mile sphere of darkness that will rip anything apart that gets to near including whole stars with powerful gravitational pull.