You may be surprised if you are informed that a Black Hole was once a star. Black and a star? Really?? This amazement might be because we have always been used to associate light with the star because of the nursery rhyme,
Twinkle, twinkle little star…
So in our mind twinkling and a star is indispensable. But in that rhyme, there is a half-truth. A star can be little but cannot be twinkling forever.
If you are really interested to know what actually black holes are, then don’t miss this episode. Hello and welcome to another episode of random thoughts.
The death of large stars leads to black holes because a star’s gravity will overwhelm the star’s natural pressure that it maintains to keep its shape. When the pressure from the nuclear reactions collapses, gravity overwhelms and collapses the star’s core, and the star’s other layers are thrown off into space, and this process is also known as a supernova. The remainder of the core collapses, a spot overcome by density and without volume – a black hole.
The First Black Hole Wasn’t Discovered until X-Ray Astronomy was Used.
Cygnus X-1 was the first black hole discovered in the 1960s, and it’s 10 times more massive than the Sun.
Black holes are some of the strangest and most fascinating objects found in outer space.
They are objects of extreme density, with such strong gravitational attraction that even light cannot escape from their grasp if it comes near enough.
There are Three Categories of Black Holes.
1) Primordial Black holes – These are the smallest of black holes and range from an atom’s size to a mountain’s mass.
2) Stellar Black Holes – These are the most common of black holes and they can be up to 20 times more massive than the Sun. There is also a variety of these all over the Milky Way.
3) Supermassive Black Holes – These are the largest of black holes, being more than 1 million times massive than the Sun.
Much like a black body in thermodynamics, a black hole is a region of space that pulls everything in but prevents anything from escaping, even light. The reason it is called a “black” hole is that it sucks up all the light that hits its border and reflects nothing. Formed when an amply compact mass deforms space and time, a black hole has a defined surface known as the “event horizon” which marks the point of no return.
The “Event Horizon” as it is called in physics, is the border of the black of hole. It’s the point of no return. Before that point, you can still escape. After that point…not a chance.
Black Holes Are Funky
Let say someone falls into a black hole and there’s an observer that witnesses this. The person who fell into the black hole, time slows down for him relative to the person watching. This is explained by Einstein’s Theory of General Relativity, which states that time is affected by how fast you are going when you’re at extreme speeds close to the light. Just as a clock runs a bit slower close to sea level than up on a space station, clocks run really slow near black holes. It all has to do with gravity.
Stephen Hawking says,
“The existence of radiation from black holes seems to imply that gravitational collapse is not as final and irreversible as we once thought. If an astronaut falls into a black hole, its mass will increase, but eventually, the energy equivalent to that extra mass will be returned to the universe in the form of radiation. Thus, in a sense, the astronaut will be ‘recycled’. It would be a poor sort of immortality, however, because any personal concept of time for the astronaut would almost certainly come to an end as he was torn apart inside the black hole! Even the types of particles that were eventually emitted by the black hole would, in general, be different from those that made up the astronaut: the only feature of the astronaut that would survive would be his mass or energy.”
Black Holes glow like a hot body and the smaller they are the more they glow. So, paradoxically, smaller black holes might actually turn out to be easier to detect than large ones!
Moreover the lower the mass of black hole, the higher its temperature. So as the black hole loses mass, its temperature and rate of emission increase, so it loses mass more quickly. What happens when the mass of the black hole eventually becomes extremely small is not quite clear but the most reasonable guess is that it would disappear completely in a tremendous final burst of emission, equivalent to the explosion of millions of Hydrogen bombs.
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