Black Holes
What is dark hole?
February 3, 2019
A dark hole is the other name given to black hole whose gravitational pull is so strong that even light cannot shine once swallowed in the hole. This is the reason why it is dark, invisible to us, and quite difficult to detect. But the term is getting unpopular today because of the so-called "Hawking radiation" (HR). HR is an electromagnetic, black body radiation which, according to the theory, is emitted by a black hole due to the black hole capturing one of a particle-antiparticle pair created spontaneously near to the event horizon until it ran out of energy. It can be detected and is visible to us through our telescopes as intermittent flashes of light, blinking on and off.
What Are Blackholes?
February 1, 2019
Black holes are regions in our Cosmos where if an object falls in, it can't get out. They are also called sinkholes because even light that passes through it has no way of getting out.
They are highy compact astronomic objects made from violent cosmic explosions of massive stars. Within the region of a black hole, there is a mass that is comparable to the size of our Solar System.
At the center of our Milky Way Galaxy lies Sagittarius A, believed to be the location of a black hole, which is around four million times the mass of our Sun, 30,000 light years away from us and 24 million kms (k1.5 million) miles across.
A black hole is formed as a result of a collapse of a massive star. The largest aging known today is the Red Supergiant Star (RSS). When a star is nearing the end of its life, it implodes, an event called "supernova."
Black holes can be big or small. The smallest black holes are as small as just one atom but have the mass of a large mountain.
Another kind of black hole is called "stellar." Its mass can be up to 20 times more than the mass of the sun.
The largest black holes are called "supermassive" with masses that are more than one million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center.
A small black hole may appear at first. The remnant of a supernova becomes a neutron star with a total diameter of around 20 kilometers (12.5 miles), which is close to 1.5 times the mass of our Sun.
If a neutron attracts more massive stars, then, it collapses and turns into a small black hole.
But because of its strong gravitational field, it can continue to attract smaller-sized matter and even huge stars around it, making it grow larger and eventually develop into a full-size, much heavier, massive black hole.
A black hole colliding with another black hole does not annihilate each other. On the contrary, the two form a much larger and stronger black hole.
This is how a black hole grows over time and it continues to grow by absorbing mass from its surroundings. Black holes have been with us from the very beginning and they continue to grow and exist for eternity.
Scientists are now watching whether Sagittarius A will continue to grow even more massive than what it is today.
Black holes are essential parts of the beginning and evolution of our universe. They also form part of our life and existence. They affect our thoughts, feelings, aspirations, dreams, and behavior towards Nature and towards each other.
Will we be affected when a nearest star implodes?
Astronomers estimate that for Earth's ozone layer to experience damage from a supernova, the blast must occur less than 50 light-years away. All of the nearby stars capable of going supernova much farther than this.
To make it easier to compare distances, our nearest star is Proxima Centauri. It is about 4.24 light years away from us. But it is not likely to become a supernova. But if a star at that distance would go supernova, there would be a very heavy damage here on Earth.
Our star, the Sun, is not massive enough to become a supernova. Instead, in about 5 billion years it should dramatically expand to become a red giant star that can fry and eventually destroy Earth.
Our Sun is also actually too small to develop into a black hole. It does not contain enough matter to exert that kind of gravitational force on itself. A star has to be more than about 10 times the mass of our Sun to become a black hole.
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(Note: Black holes and supernovae are discussed lengthily in Chapter 11 of my book "The Future of Humanity from the Perspective of Quantum Physics" together with dark matter and dark energy.