Astronomy: experts analyze the end of the sun

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Depiction of eruptions on the sun

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NASA

In about three and a half billion years, our Sun will begin to cool at the surface, puffing up into a red giant star - potentially engulfing all of the inner planets, including Earth.

This horror scenario is not new, but astronomers have now determined the time and course of this catastrophe more precisely than ever before.

The result: When the sun is eight billion years old, its surface will reach a maximum temperature - which is only about 20 degrees higher than today's value of 6045 degrees Celsius, experts from the European Space Agency ESA report in the journal "Astronomy & Astrophysics".

Then it begins to cool and expand into a red giant.

Only when there is no longer any nuclear fusion inside - at an age of ten to eleven billion years - does the red giant collapse into a white dwarf star just about the size of the earth, which slowly cools down over billions of years.

"Only when we understand our Sun - and there is still a lot we don't know about it - can we expect to understand all the other stars in our Milky Way," explains Orlagh Creevey from the Observatory Côte d'Azur in France, first author of the Work.

Highly precise readings

Creevey's team analyzed recently published data from the "Gaia" satellite, which has been observing billions of stars with several telescopes since 2014.

"Gaia" records the movement, size, temperature, mass and chemical composition of stars of different ages - and also provides insights into the life history of our sun.

We only see our sun at the present time of its development, 4.57 billion years after its formation.

Only the observation of many sun-like stars of different ages allows experts to predict the development history of our central star.

In a first step, the experts searched the »Gaia« data for the stars with the most precise values.

"We wanted to have the cleanest possible data set with high-precision measurements at our disposal," says researcher Creevey.

In a second step, the team filtered out all those stars from this selection that resemble our sun in terms of their mass and chemical composition.

The bottom line is that although all of these stars are similar to the sun, they are very different in age.

As long as stars burn hydrogen into helium in their interior and thus generate their radiation, their mass and composition change only slightly.

The situation is different when it comes to size and temperature: Both are slowly increasing.

Since the stars are similar to the sun, but are of different ages, Creevey's team was able to determine how these stars - and thus our sun - evolved over time.

The question of life in our solar system

In addition to these analyses, the experts selected all those stars from their data that also resemble the sun in terms of temperature and size - and are therefore also about the same age as our central star.

They found a total of 5883 "solar analogues" in this way.

The list is valuable to astronomers around the world.

The precise observations of these stars can answer the question of how "normal" our sun is.

Or whether the emergence of life on Earth depended on the fact that the sun has special properties that distinguish it from other stars.

jme/dpa