Now we know how old the Sun is and when it "will die"

Now we know how old the Sun is and when it “will die”

The data acquired by the Gaia mission of the Space Agency Europe allow us to have a more precise idea of ​​the evolution of the Sun in the future

How will the Sun evolve in the future? What will be the date of his “death”? Now astronomers have new data available to answer these questions, thanks to the Gaia mission of the European Space Agency and the new information collected, which was published on 13 June.

Gaia is a spacecraft launched by ESA in 2013 for a mission that should continue until 2025. Its main objective is to collect data on the stars of our galaxy: from measuring the position to the distance from us, up to their movement. By comparing and studying these data – in particular those relating to the third important release, of June 13 – it was possible to discover something more about the star around which the Earth rotates, the Sun.

While the mass of the stars changes relatively little during his life, its temperature and size vary greatly as the years go by. These variations are determined by the type of nuclear fusion reactions that take place inside the star. To relate the properties of the hundreds of stars that we are able to observe, there is a diagram – known as Hertzsprung-Russell diagram – conceived at the beginning of the twentieth century by the two astronomers Ejnar Hertzsprung and Henry Norris Russell. This model chorrors the intrinsic brightness of a star with its surface temperatureand is therefore unable to reveal how stars evolve during their long life cycles.

The Sun, today, has 4.57 billion years. It is in a “comfortable middle age, melting hydrogen into helium and generally being in a rather stable situation, even stationary,” they explain from the ESA. When the hydrogen runs out in the core, the changes in the fusion processes will begin and the star will turn into one red giant, heading towards his “death”. To understand when this will happen you need to have information on its mass and its chemical composition. This is where the Gaia data and the HR diagram come into play, which allows you to to correlate the history of other stars with that of the Sun..

The analysis was done by Orlagh Creevey, of the Côte d’Azur Observatory, and by the collaborators of the Coordination Unit 8 of Gaia. They mostly used data relating to stars with surface temperatures between 3,000 and 10,000 Kelvin (the Sun today has a surface temperature of about 6 thousand Kelvin): they are the ones with the longest life and can therefore reveal more information on the history of the Milky Way. Then they focused on celestial bodies with the same mass and chemical composition as the Sun. – the criteria included a sample of 5,863 stars – managing to draw a line on the HR diagram that represents its evolution from the past to the future.

The Sun will reach his maximum temperature when it “turns” about 8 billion years (therefore in about 3.5 billion years). Then it will cool down and it will become a red giant star: this will happen around his 10-11 billion years (therefore in about 5.5 or 6.5 billion years). Eventually she will “die”, transforming into a white dwarf. “If we can’t understand our Sun – and there are many things we don’t know about it – how can we think we understand all the other stars that make up our wonderful galaxy?” Explained Creevey.

August 28

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