Black Holes in Space

We all have surely heard about the general theory of relativity, which was proposed by Albert Einstein. His theory states that gravity is a geometric property of space and time (known as spacetime) which is related to the subject's mass, energy and momentum. So when a star of huge mass, energy and momentum is compressed into a compact small space, an infinite spacetime and a massive gravitational pull is created. The spacetime curvature caused by this mammoth gravity is so huge that even light gets sucked into this space. When stars of the solar system meet such a fate, they are termed as black holes.

How are Black Holes in Space Formed?

In the life cycle of a star, there is a constant nuclear fusion at its core which generates photons through electromagnetic radiations. This radiation is responsible for the outward pressure that perfectly balances the pull of gravity from the mass of the star. But at the fag end of the star's life, when the nuclear fuel of the star starts diminishing, the outward pressure starts to reduce. Consequently, the inward gravitational pull increases manifold, thereby shrinking the star inward. Eventually, the core of the star collapses and becomes a black hole.

Facts about Black Holes

• One of the most basic facts about black holes, based on Einstein's theory of general relativity, is that the objects falling into a black hole never reappear. The gravity of a black hole is so intense and powerful that a gravitational time dilation happens, which causes time to stop.
• A black hole has two sections: singularity and event horizon. The event horizon is the surface of the black hole and the singularity signifies the core of the black hole. Anything to get sucked into the black hole needs to be in the vicinity of the event horizon, else the object will not be sucked in. Event horizon is also known as - "point of no return". Singularity is the sole point of suction where the volume is zero and density is maximum. This is the point of infinite spacetime curvature.
• The mass and size (radius of the event horizon) of a black hole are directly proportional to each other. For instance, if one black hole is 10 times heavier than another black hole, its radius also ought to be 10 times larger than the other. In fact, if there is a black hole with a mass equivalent to Sun, it will have a radius of 3 kilometers only! The radius of this event horizon is also known as the Schwarzschild radius which can be calculated by the formula: r=2GM/c² (where r: Schwarzschild radius, G: gravitational force, M: mass and c: speed of light or escape velocity.)
• With time, black holes keep shrinking in size as they constantly emit x-ray radiations constantly. After some while, they nearly evaporate.
• Only stars 10-15 times as massive as Sun can transform into black holes as they can get compressed to the Schwarzschild radius. Smaller stars become white dwarfs or neutron stars.
• And last but not the least, even light gets sucked into the black hole once it crosses the event horizon. To escape from a black hole, one needs an escape velocity greater than that of light, which is not possible!
• Currently, there are 14 known black holes in the universe.
• The black hole nearest to earth is known as V 4641. This black hole is 1600 light years (16 quadrillion Km) away.
• The next closest black hole is Cygnus X-1 which is about 8000 light years (80 quadrillion Km) away.
• There are 2 kinds of black holes: Stellar black holes and super massive black holes. A stellar black hole is a small one which is formed whenever a star collapses. Whereas, a super massive black hole is an aggregation of many black holes. A super massive might contain a million to trillion Suns!
• At the center of the Milky Way galaxy, there is a massive black hole, which weighs about 4 million solar masses. Fortunately it is 30,000 light years away from earth and hence no need to get worried about being sucked in!

NASA's Research on Black Holes

There has been a lot of ongoing research on black holes. NASA is exploring more into the mysteries of these black holes with the help of its space missions. XMM-Newton is a space telescope that was launched into the Earth's orbit in 1999 by NASA and European Space Agency. This telescope has helped the scientists a great deal in unraveling facts about black holes. This is because the telescope can observe the universe in a light containing high energy x-rays that are mostly emissions of black holes. The other space mission to be launched by NASA, is LISA (Laser Interferometer Space Antenna). LISA has 3 spacecraft which will orbit the Sun, all of them connected by laser beams. This space mission will aid in understanding the concept of gravitational waves of black holes. LISA will get launched in 2015. Not to miss an interesting fact, NASA's Galaxy Evolution Explorer, in 2006, had caught an interesting snapshot of a giant black hole gobbling up a star! This was the first of all times when the astronomers saw the entire process of a star being sucked into the black hole in space.

So you must be wondering what if our Sun becomes a black hole? Relax! Our Sun is not so massive enough to become a black hole. It might become one white dwarf or a neutron star after several billion years which is definitely not anytime in near future! Isn't it? Hope you readers got to learn interesting facts on black holes. No wonder, real black holes are the most amazing facts about the universe. The mysteries unfolded in the world of astronomy is just a never ending saga. So true!