One day our Sun will die.

Since we happen to be inhabitants of the planetary system of the Sun, the question of when and how this will happen is of great interest to us.

Of course, it’s unlikely that we’ll be there to see it… but, you know, this is our home. We want to know what will happen in the end. Curiosities aside, models of stellar evolution can help us understand the cosmos and our place in it.

“If we don’t understand our own Sun – and there’s a lot we don’t know about it – how can we hope to understand all the other stars that make up our wonderful galaxy,” says astronomer Orlagh Creevey of the Côte d’Azur Observatory in France.

We already know in detail what will happen in the future of our Sun. It will continue to heat up over the next billion years, eventually running out of hydrogen to fuse into its core.

The heart will begin to contract, a process that brings more hydrogen to the region immediately around the heart, forming a hydrogen shell. This hydrogen then begins to fuse, spilling helium into the core, in a process called shell burning.

During this time, the Sun’s outer atmosphere will expand a lot, possibly even into Mars’ orbit, turning it into a red giant. Eventually it will run out of hydrogen and helium, eject all of its outer material to form a planetary nebula, and the core will collapse into a white dwarf, which could take billions of years to cool completely.

But when the main sequence ends depends on the individual characteristics of each star. When it comes to our own Sun, the ballpark figure for when things will go south could always use more evidence.

The best way to find it is to search the Milky Way for Sun-like stars at different stages of their lives, then fit them into a timeline that models the past and future of our own star.

With the latest release of data from the European Space Agency Gaia Milky Way mapping project, we now have the most detailed timeline of the Sun’s life to date.

Gaia’s primary mission is to map the Milky Way with the greatest accuracy to date, and it is equipped with a suite of instruments for this task. It tracks the positions and movements of stars in the sky, while taking detailed observations of each star’s brightness and spectral classification.

These values ​​can be used to determine factors such as chemical composition and temperature. They can also be plotted on a graph known as Hertzsprung-Russell diagramwhich gives an estimate of the age of the star.

The mass of a star, you see, doesn’t really change with age; but its temperature does, quite significantly, depending on the nuclear fusion that occurs in the stellar core, which is observed as changes in luminosity.

Our Sun is classified as a G-type main sequence staror yellow dwarf (even though it’s not really yellow), and is a fairly typical example of its kind.

It is about 4.57 billion years old, about half its main-sequence lifespan. It is also capable of central thermonuclear fusion, generating a surface temperature of 5,772 Kelvin. This means that looking at other G-type stars should give us a pretty good idea of ​​how our Sun might continue to burn fuel and when it might possibly die out.

Creevey and his team first started combining Gaia data because they wanted accurate observations of stars with relatively “cooler” temperatures between 3,000 and 10,000 Kelvin. That’s because low-temperature stars tend to be smaller and live longer than hotter ones. looking at cooler stars can therefore potentially tell more about the history and stellar evolution of the Milky Way and the wider Universe.

Since this temperature range includes stars like the Sun, the data could be used to focus on stars with similar mass and chemical composition to the Sun. This resulted in 5,863 Sun-like stars on the entire Hertzsprung-Russell diagram, from very young to very old.

By identifying only the stars most similar to the Sun, Creevey and his colleagues were able to confirm the time of its disappearance.

Overall, consistent with previous projections of the Sun’s lifetime, its temperature will peak at about 8 billion years. It will turn into a red giant star around 10 to 11 billion years.

Life on Earth, for the record, is only about a billion years old, unless we do something catastrophically stupid, or something catastrophic happens to us. This is because the Sun’s luminosity increases by approximately 10% every billion years; which means that its temperature also increases. This change seems small, but it will make Earth uninhabitable for life as we know it.

So it’s cheerful. But there is still work to be done. Gaia’s new catalog of Sun-like stars might tell us more about how and why we’re even here to begin with. We can tell if Sun-like stars all behave the same way, for example. And, more importantly, look for more planetary systems that resemble the solar system.

So far, we have not found any systems that seem capable of supporting technologically advanced life as we know it. But the answers are there. If we can find them.

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