• The sun will eventually grow and cool until it becomes a "red giant", according to our partner The Conversation.

  • But when that happens – in 4.5 billion years – there will likely be no more humans on Earth to watch the spectacle.

  • This analysis was conducted by Olga Suarez, research engineer in astrophysics at the University Côte d'Azur.

The Sun is not going to explode.

This answer might 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 that is called " main sequence.

This means that for 4.5 billion years, our star will continue as before, to produce nuclear reactions in its core which make it 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 begin to use the hydrogen that is around the core as fuel.

It's as if in a house we had no more wood for the fireplace and we decided to burn the chairs!

And in this new stage, the Sun will grow and cool, becoming 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 won't be any humans around at this time to behold the spectacle, we know it won't be the Sun's last farewell yet.

There will still be a few hundred million years during which the Sun will begin to use another atom as fuel in addition to hydrogen: helium.

It's as if in the house where we had started to burn the wooden chairs, we decided to also take the curtains and the tablecloths!

During this last stage, the outer layers of the Sun will slowly separate from the center forming 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 image), and they are too faint to be observed with the naked eye.

Our "SUN" file

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 detected this jet by observing it with a set of telescopes.

It was the first time that a jet of this type was observed in a planetary nebula, and it made us think that perhaps the Sun will also have, at the end of its life, a mini-explosion of this type.

In any case, this will happen in almost 5 billion years, so there is nothing to worry about now.

Our Sun will have a rather calm and splendid end of life.

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This analysis was written by Olga Suarez, research engineer in astrophysics at the University Côte d'Azur.


The original article was published on

The Conversation website

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