At some point in the very distant future for us, the Sun will die . Stellar evolution models help us understand the cosmos and our own place in it. In the case of our star, we already know in some detail what will happen to it in the future: when its fuel (hydrogen) runs out, it will stop generating heat through nuclear fusion and its core will become so destabilized that it will end up contracting while the outer zone shrinks. will expand as it begins to cool down.
This expansion movement in which even the outer atmosphere of the Sun could reach up to the orbit of Mars, will devour everything around it. Finally, once it runs out of hydrogen and helium, it will leave behind a planetary nebula, and the core of the Sun will end up becoming a white dwarf that would take billions of years to cool completely. Of course, this is still about 5 billion years away (and considering that our planet is barely 4.5 billion years old, that means we have a long, long, long time left).
If you are wondering if the Earth would survive if it were not hit by this expanding tide from the Sun, the truth is that it would be impossible for us to survive without the Sun as we know it now. The heat and radiation from the sun would boil the oceans and atmosphere and it is even likely that the planet itself would also turn into a possible ball of lava. By that time, humanity should have already left Earth and found another solar system to live in.
But let’s return to the Sun still alive.
How do scientists calculate the life of the Sun?
Where does this rough figure come from? You will ask yourself. To calculate how long our star has to live, we need, first of all, to know the mass of the Sun, a fact that we can easily count on: 2 x 10^30 kg (or a 2 with 30 zeros). We also need to know its luminosity or brightness, which is 3.8 x 10^26 watts (which is the rate at which the sun emits energy).
It can be estimated by assuming that the Sun will “die” when it runs out of energy to continue shining . The time for this to occur is approximately the total energy the Sun has that can be converted into light, divided by the rate at which the Sun emits energy.
Once we have these two numbers, we will use one of the most famous equations in physics: E = mc2 . Thus, using Einstein’s famous formula for the conversion between mass and energy we have that the energy available in the sun is: e = 0.007 xm c2 where c is the speed of light and M is the amount of mass in the sun that is capable of undergoing the above nuclear reactions.
A 4.75 billion year old yellow dwarf
However, the Sun works by nuclear fusion generating helium through the fusion of hydrogen, but not the entire surface of the Sun has the right conditions for nuclear fusion. This circumstance only occurs in the center of the Sun given the enormous amount of energy that this process needs. Therefore, if only 10% of the Sun’s mass is the one that allows nuclear reactions, we obtain a different figure. The calculation gives us an approximate value of 10 billion years for the life of the sun.
Since the mass of a star does not change as it ages, but its temperature does, and quite significantly, based on nuclear fusion taking place in the stellar core, which is observed as changes in brightness, we know that our Sun he is about halfway through his life. It is a G-type main sequence star that is about 4.57 billion years old, or about halfway through its main life cycle , since stars like our own burn, effectively, for about 9 to 10 billion years. .
Referencia: Ask an Astronomer, Astronomy Department at Cornell University.
Gaia reveals the past and future of the Sun / ESA.int
Computing the Sun’s Luminosity and Lifetime, University of Arizona.
SOHO Instrument Consortium
