When the sun dies, the sun first becomes a red giant, then a white dwarf. The good news is that people won’t notice it anymore.
Manchester – There are different types of stars in space: red giants, white dwarfs and yellow dwarfs. All these celestial bodies have one thing in common: they radiate independently – in contrast to planets, which only reflect the light that falls on them. Stars, on the other hand, can end up in different ways, depending on their mass.
Our sun is a yellow dwarf, which only appears so large to us because the earth is so close to it: the blue planet is about 150 million kilometers away from the sun. This distance is just right to make liquid water and thus livable conditions on earth possible. But in the distant future the sun will no longer be the star that makes the earth worth living in. That’s what researchers have found who are studying how the sun will one day die.
The sun will die in five billion years – mankind sooner
That day is still a long way off: it will still be five billion years before the sun comes to an end. But then there will be a tremendous spectacle – which the people on earth will no longer experience, since the earth will no longer be habitable before then. But from the front: The sun gets hotter the older it gets. And due to the heat, the oxygen content of the earth’s atmosphere decreases – In a billion years life on earth will no longer be possible.
That’s why mankind doesn’t notice what’s going on with the sun: In about five billion years, the sun will have used up a large part of its “fuel”, which it burns in a nuclear fusion, and will expand into a red giant star. The outer layers of the sun will expand, engulfing the planets Mercury, Venus, Earth and Mars.
When a star dies, it ejects a mass of gas and dust – its envelope – into space. The shell can account for up to half the mass of the star. In the process, the star’s core is exposed, which by this point will run out of fuel and eventually shut down before finally dying.
The sun will shrink to a white dwarf star
A 2018 study has shown what will happen to the Sun afterwards: it will shrink from a red giant star to a white dwarf star – very small and very hot – and will shed its gas envelopes into space in the process. This will probably result in a planetary nebula.
“When a star dies, it ejects a mass of gas and dust — its envelope — into space. The shell can account for up to half the mass of the star. This exposes the core of the star, which is at this point running out of fuel and eventually shutting down before finally dying,” said University of Manchester astrophysicist Albert Zijlstra. He is one of the authors of the study, in a communication.
Dying sun will create a planetary nebula
“Only then does the hot core light up the ejected shell brightly for about 10,000 years – a short period of time in astronomy. This makes the planetary nebula visible. Some are so bright they can be seen from extremely large distances of millions of light-years, where the star itself would be far too faint to see.”
Planetary nebulae are widespread in the observable universe. The best-known examples include the Helix Nebula (NGC 7293), the Cat’s Eye Nebula (NGC 6543), and the Ring Nebula (NGC 6720). (tab)