May 27, 2020

What will happen to the Sun when it dies? | Science

He Sun It's a pretty mediocre star, let's be clear on this. It is mediocre both in size and in the light it emits and in the rest of its characteristics. It is neither the smallest nor the largest, nor the brightest nor the least luminous. But it is ours! It is estimated that his life will be about 10,000 million years and as it was formed approximately 4.6 billion years ago, he has the same.

Right now, since he is halfway through his life, he is burning hydrogen. When we say burn it means that in its core that is very, very, very hot (15 million degrees) and at a great deal of pressure, the original hydrogen is fusing to produce helium, which is a slightly larger and slightly heavier element. This will continue to happen almost until the end of his life.

In that process of burning hydrogen, from Earth what will be noticed is that the Sun is increasing in size and luminosity little by little. It is not an excessively significant increase but it is something that already happens. In life, the Sun has grown by approximately 20%.

When the hydrogen is over, it will begin to burn the next element that is helium and that is when we will really be at the end of the star's life. But for this there are still about 5,000 million years. The current phase is called the main sequence and will end when the hydrogen is finished. Then, it will enter the phase called the red giant that is when it will begin to burn helium.

The process in the end will be as follows: when the hydrogen runs out, the nucleus will begin to compress

The process in the end will be as follows: when the hydrogen runs out, the nucleus will begin to compress. To understand what will happen from that moment on, it is important to keep in mind that the star survives because there are two opposing forces that act on it. On the one hand, the mass of the star pushes inwards by gravity but, on the other hand, nuclear fusion reactions give off a lot of energy and that creates a pressure outward, in the opposite direction to gravity. The nucleus is currently in equilibrium due to the action of these two opposing forces. When the hydrogen runs out the energy that had been pushing out disappears and that is why the nucleus will collapse.

When contracted, the nucleus will get very hot until it reaches enough temperature to start burning helium, an element that needs a higher temperature to merge because it is a little heavier than hydrogen. While the Sun's core contracts to fuse helium, the layers around the core (let's think inside the Sun as if it were an onion) will burn hydrogen, which will heat them and make them expand enormously. That is why this phase is called the red giant. The red color comes because the outer layers will cool as they expand.

There is one thing that researchers do not know yet and it is if that expansion that will be brutal and that will make the Sun reach a size between 150 to 200 times what it has now, will engulf the Earth. We do know that it will grow so much that Mercury and Venus will be swallowed but that of the Earth is not very clear. Anyway, even if you don't eat us, the temperature will be so high that life on our planet will be impossible from many millions of years before.

A woman enjoys the arrival of summer with the sunset T

A woman enjoys the arrival of summer with the sunset T EFE

Then, we will have the nucleus compressing a lot and starting to burn helium and at the same time the outer layers growing, growing, growing. And how will the matter end at the end of his life? The nucleus will burn all the helium it has, it will contract and heat again. But it will never reach enough temperature to burn the next heaviest element, carbon. The end will occur when all these outer layers are ejected into the space in what is called a planetary nebula that is a very spectacular gas and dust ring-shaped wrap and in the center a very dense ball will be left (about the size of Earth) which is the core of the star and is called white dwarf. After a few thousand years, this white dwarf will cool down because it will not generate energy, it will go out and that will be the end of the Sun. As a consolation we know that we are made of atoms from stars that died before our Sun.

Ada Ortiz Carbonell She is a PhD in Physics, a researcher at the University of Oslo in the field of solar astrophysics and data scientist at Expert Analytics.

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