- 3704 - SUN - the future is not so bright? - Within the Gaia satellite data, astronomers looked for stars with temperatures, surface gravities, compositions, masses and radii that are all similar to the present-day Sun. They found 5,863 stars that matched their criteria. Plotting this data shows us the evolution of all the stars.
--------------------- 3704 - SUN - the future is not so bright?
- We take our Sun for granted . It gives us heat and light every day, year after year. But, we have to realize tht the Sun has a lifetime too. It is burning hydrogen into helium. Eventually all the hydrogen will be used up. The Sun will start the life ending process too.
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- We have a satellite that is studying our Sun’s past and future. The latest data from Europe Space Agency’s star mapping “Gaia” satellite mission, can do just that for the Sun. By accurately identifying stars of similar mass and composition, astronomers can see how our Sun is going to evolve in the future.
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- Gaia’s third major data release (DR3) was on June 13, 2022. One of the major products to come out of this release was a database of the intrinsic properties of hundreds of millions of stars. These parameters include how hot they are, how big they are, and their masses.
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- Gaia takes exceptionally accurate readings of a star’s apparent brightness, as seen from Earth, and its color. Turning those basic characteristics into the intrinsic properties of a star.
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- Astronomers are classifying the appearance of ‘spectral lines’ measured by Gaia‘s spectrometers. These are dark lines that appear in the rainbow of colors produced when a star’s light is split with a prism. The stars are ordered according to the strength of these spectral lines. This order was subsequently found to be directly related to the temperature of the stars. It was later discovered that the width of the lines was related to the luminosity and age of a star.
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- Correlating these two properties allows every star in the Universe to be plotted on a single diagram known as the “Hertzsprung-Russell (HR) diagram“. It has become one of the cornerstones of astrophysics. Devised independently in 1911 by Ejnar Hertzsprung and in 1913 by Henry Norris Russell, an HR diagram plots a star’s intrinsic luminosity against its effective surface temperature. It reveals how stars evolve throughout their long life cycles.
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- While the mass of the star changes relatively little during its lifetime, the star’s temperature and size varies greatly as it ages. These changes are driven by the type of nuclear fusion reactions that are taking place inside the star at the time.
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- With an age of around 4.57 billion years, our Sun is currently in its comfortable middle age, fusing hydrogen into helium and generally being rather stable. That will not always be the case. As the hydrogen fuel runs out in its core, and changes begin in the fusion process, it to swell into a “red giant star“, lowering its surface temperature in the process.
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- Exactly how this happens depends on how much mass a star contains and its chemical composition. This is where “DR3” comes in. The surface temperatures of between 3,000 Kelvin and 10,000K which is where the longest-lived stars in the Galaxy exist and hence can reveal the history of the Milky.
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- Those stars that had the same mass and chemical composition as the Sun were plotted on the diagram. The ages were different and the stars they selected ended up tracing out a line across the H-R diagram that represents the evolution of our Sun from its past into its future. It revealed the way our star will vary its temperature and luminosity as it ages.
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- Our Sun will reach a maximum temperature at approximately 8 billion years of age, then it will cool down and increase in size, becoming a “red giant star” around 10 billion years of age. The Sun will reach the end of its life after this phase, when it eventually becomes a dim “white dwarf star”.
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- Finding stars similar to the Sun is essential for understanding how we fit into the wider Universe. The Sun is our nearest, most studied star yet its proximity forces us to study it with completely different telescopes and instruments from those that we use to look at the rest of the stars. This is because the Sun is so much brighter than the other stars.
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- Within the Gaia data, astronomers looked for stars with temperatures, surface gravities, compositions, masses and radii that are all similar to the present-day Sun. They found 5,863 stars that matched their criteria.
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- Some of the questions yet to be answered to include is do all solar analogues have planetary systems similar to ours? Do all solar analogues rotate at a similar rate to the Sun?
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- With data release DR3, Gaia’s supremely accurate instrumentation has allowed the stellar parameters of more stars to be determined more precisely than ever before. And that accuracy will ripple out to many other studies. Knowing stars more accurately can help when studying galaxies, whose light is the amalgamation of billions of individual stars.
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October 11, 2022 SUN - the future is not so bright? 3704
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