The sun is not going to explode. This answer may reassure you, but I assure you that even if it does not explode, no one will want to be close to our star towards the end of its life, in 4.5 billion years.
Our sun is a rather small star and not too hot compared to other stars. It is about halfway through its life: it was formed 4.5 billion years ago, and it will still live a similar time in its current state, the phase called the “main sequence”. This means that for 4.5 billion years, our star will continue to produce nuclear reactions at its core, which will cause it to shine and warm us.
But one day, the fuel that allows the Sun to make these nuclear reactions in its core, hydrogen, will run out. And at that moment, instead of ending its life, the Sun will start using the hydrogen that is around the core as fuel. It is as if we in a house had no more firewood for the fireplace and we decided to burn the chairs! And in this new phase, the Sun will grow and cool and become a “red giant”.
Red giants are huge stars. When the Sun is a red giant, in 4.5 billion years, our planet will be inside it!
But even though there will be no people nearby at this time to see the show, we know it will not be the Sun’s last farewell yet. There will still be a few hundred million years in which the Sun will begin to use another atom in addition to hydrogen as fuel: helium. It is as if in the house where we had started burning the wooden chairs, we also decided to take the curtains and tablecloths!
During this last phase, the outer layers of the Sun will slowly separate from the center and form a nebula, which will be illuminated by this central core, this is called a “planetary nebula”.
Planetary nebulae have nothing to do with planets, they were named during the 18th century before we really knew their nature. They are among the most beautiful objects in the sky when observed through a telescope (see picture), and they are too faint to be observed with the naked eye.
Recently, in 2015, we discovered that there is still a chance that the Sun will produce a mini-explosion with the ejection of a very fast jet of material, at a speed of more than 100 km / s. We observed a sun-like star that has just become a planetary nebula, and we discovered this jet by observing it with a set of telescopes. It was the first time a jet of this type was observed in a planetary nebula, and it made us think that the Sun might also want a mini-explosion of this type at the end of its life.
It will at least happen in almost 5 billion years, so there is nothing to worry about now. Our sun will have a rather calm and wonderful end to life.
This analysis is written by Olga Suarez, research engineer in astrophysics at the University of Côte d’Azur.
The original article was published on the site of The conversation.