The sun will not last forever. Scientists can foresee the future of the star that gives energy to our solar system. However, we will not be alive to witness it.

The ESA’s Star Mapping GAIA project now provides a glimpse into the Sun’s future by detecting stars of similar mass and composition and forecasting how our Sun will evolve in the future. Despite the fact that the Earth has less time than the Sun, let us investigate what will happen in the future.

We already know that the Sun is powered by ‘nuclear fusion.’ Over the next few billion years, the Sun will continue to heat up, eventually depleting the hydrogen at its core. The core would then contract, bringing the hydrogen together to create the nucleus.

While the core is contracting, the Sun’s outer atmosphere begins to expand significantly, consuming Earth and even engulfing Mars, transforming the Sun into a red giant.

When the Sun’s core runs out of hydrogen and helium, it will eject all of its outer material, becoming a planetary nebula, while the core collapses into a white dwarf.

While this is based on how other stars have grown over time, it is crucial for Earth dwellers to have an idea about our planet’s and the Sun’s destiny.

Figure 1. Sky map of stellar age obtained for Gaia Data Release 3, showing the average age of the stars in our Galaxy, with blue representing the younger stars and red representing the older stars. Most of the oldest stars are found outside the galactic disk. The age was derived with the Final Luminosity Age Mass Estimator (FLAME). Shown in this map is a random selection of 10 million stars from Gaia DR3. Credits: ESA/Gaia/DPAC – CC BY-SA 3.0 IGO. Acknowledgements: created by O.Creevey, M. Fouesneau, and the Gaia group at MPIA.

The third and most recent data release (DR3) from ESA’s GAIA mission sheds light on the Sun’s life cycle. “One of the key results of this release was a database of millions of stars’ intrinsic attributes. These factors include their temperature, mass, and the amount of mass they contain.”

Figure 2. Hertzsprung-Russell diagram with young massive star sample (OBA), intermediate mass sample (FGKM), low-mass ultra-cool dwarfs (UCD), evolved carbon-rich stars and solar analogues. Credits: ESA/Gaia/DPAC – CC BY-SA 3.0 IGO, based on Gaia Collaboration, Creevey, et al. 2022.

The GAIA mission takes precise readings of the star’s apparent brightness and colour from Earth and plots them on a single diagram known as the Hertzsprung-Russell (H-R) diagram.

An HR diagram plots a star’s intrinsic brightness against its effective surface temperature. It reveals how stars change over their long life cycles in this way.

While the mass of a star changes very little over its lifetime, the temperature and size of the star change as it matures, due to the sorts of nuclear fusion events that occur in the core.

Our Sun is at its middle age and stationary condition at 4.57 billion years old. However, as the Sun ages, this stability will change. That’s where the most recent GAIA mission data (DR3) comes in.

Orlagh Creevey of the Observatoire de la Côte d’Azur in France and colleagues from Gaia’s Coordination Unit 8 analysed the data for the most precise stellar observations that the satellite could provide.

Figure 3: The Gaia DR3 RVS spectra of 1046 solar analogues. Outer grey contour includes 90% of the sample. Inner grey contour contains 68% of the sample. The most prominent absorption lines are marked with vertical dashed lines. Credits: ESA/Gaia/DPAC – CC BY-SA 3.0 IGO. The image is adapted from the one presented in Gaia Collaboration, Creevey et al. 2022. Acknowledgements: Rene Andrae, Andreas Korn, Orlagh Creevey, Georges Kordopatis, Rosanna Sordo.

They concentrated their attention on stars with surface temperatures ranging from 3000K to 10000K since they are similar to the Sun, which has a surface temperature of 6000K.

Furthermore, because these are the longest-living stars in the Milky Way, they can tell the Milky Way’s history. They are also promising candidates for the discovery of exoplanets.

The scientists then filtered the results to display only stars with masses and chemical compositions similar to the Sun. The stars they chose traced a line in the H-R diagram that portrays our Sun’s evolution from its past to its future because they allowed ages to vary. This implies that the Sun’s temperature and brightness change as we age.

According to the findings, our Sun will reach its maximum temperature about 8 billion years old, then cool and expand in size, becoming a red giant star approximately 10-11 billion years old.

After this stage, the Sun will approach the end of its life and become a faint white dwarf.

How long will Earth be nearby?

While it is 8 billion years ahead of the Sun, Earth’s duration of time is significantly shorter, at 1 billion years. This is due to the Sun’s brightness and temperature growing by 10% per billion years; while 10% may seem insignificant, it would heat Earth sufficiently to make it livable for any form of life.

Orlag and his colleagues sought stars with similar temperatures, surface gravity, composition, mass, and radius to the Sun. He received 5863 stars that fit his criterion.

It also gives a ray of optimism to our way of existence, because there is always the possibility of discovering livable planets like Earth among these 5863 stars like our Sun.

We don’t know if there is a planet that could support life right now, but we’re looking.

 

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