Black Holes: Yin and Yang

By Smaran

In every end there is a beginning. For every beginning there is an end. When life is take away, life is also given. We all know that the standard black hole devours and destroys and it is the end of all things. We know that once something enters the gravitational field and has passed the point of no return, kaput. But what if i told you that a black hole actually could give life. When you think about it while factoring in the information and evidence, it starts to piece together so just here me out. The incredibly immense gravitational pull of the black hole – what we call its tidal force, the same force that the Moon exerts to cause the ocean tides (only on a much larger scale) – will tear the star apart, and devour, or accrete, the remains. But if the star is a white dwarf, the evolutionary endpoint of low- to middle-mass stars like our Sun, something interesting can happen. In these white dwarves, hydrogen fusion has already come to a halt before they get gobbled up. But as the black hole’s tidal forces simultaneously stretches and compresses the star in opposing directions in what is called a tidal disruption event, the compression can actually reignite fusion in the star’s core, even if just for a few seconds, according to new simulations. The destroyer of worlds instead feeds the spark of life.

But here’s the catch: this can only happen if it’s an intermediate mass black hole. For some reason, those seem to be missing from the Universe. There are two categories of black holes in the Universe. There are your regular stellar-mass black holes, typically below around 100 times the mass of the Sun. These are the ones whose collisions are responsible for gravitational wave observations. Then there are the supermassive black holes, ranging from a lower limit of  around 100,000 solar masses, but ranging up to millions or billions of solar masses. Sagittarius A*, the supermassive black hole at the centre of the Milky Way, is about 4 million solar masses. But the problem is that neither stellar-mass nor supermassive black holes will produce the white dwarf resurrection effect. It is basically as Goldilocks being the dwarf star and the little bear’s stuff being the teenage black holes. A stellar-mass black hole is quite physically small, which means that initially the white dwarf will engulf it; and a supermassive black hole’s tidal forces are so strong that the star will fall into it before it can be disrupted. Only the teenage sized black holes provide just enough leeway for the process to happen.

But for the sake of the article, lets just say that it actually happened. If a white dwarf was to be swallowed by an intermediate mass black hole, the reignited nuclear fusion can convert the typical white dwarf composition of helium, carbon, and oxygen into heavier elements such as iron and calcium. Simulations show that, when the white dwarf is a little farther away from the black hole, more calcium is produced; but when it’s closer, more iron is produced. Since not all of the star ends up devoured by the black hole, these elements can then be blown out into space, where eventually they’ll be incorporated into new stars. So it is basically a win win for both the black hole because it is getting more food and for the universe because it just had a couple of new stars born.

And you can make your own star for the low low price of your soul, Mc. Scrooge’s bank account (Duck Tales), and the Eye of Vishnu. If you give me that then with a little compression here, a time machine there, a white dwarf over there, and a whole lot of matter all the way over there (I don’t know why we need matter but what’s the matter with you), you will make your own little star! Batteries not included.

Like how for every beginning there is an end, this is the end of this article and this series, and thank you for reading the black holes series. If you have any ideas, please ask this email account, and no it is not my real name and my actual account.

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