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Solar-Stellar Connections

The Sun is a star. While we take that fact for granted today, the discovery that stars are objects like our Sun was a profound one. The kinship between the Sun and stars means we can learn about distant stars by studying the Sun. The reverse is also true: we are only witness to the Sun as it is now, but other stars can show us how it was during earlier stages of the Sun’s life, and how the Sun will be billions of years later.

Hot gas driven by the Sun's magnetic field shoots up from the surface in this image from the Hinode spacecraft. Researchers use what they've learned about the Sun to study similar phenomena on other stars.

Credit: Hinode, JAXA/NASA

The Sun is the Nearest Star, Other Stars are Distant Suns

The Sun turns out to be a pretty ordinary star. It’s a “main sequence” star, meaning it fuses hydrogen into helium in its core. Mass-wise, it’s above average, but it’s similar to many stars we see in the Milky Way and beyond. As a result, the Sun helps us understand a lot of other stars in the cosmos.

That’s ideal because the Sun is so close. Earth- and space-based telescopes monitor the Sun literally all the time. Solar researchers study day-to-day fluctuations in the Sun’s atmosphere and magnetic field, looking for patterns that reveal what’s going on beneath the surface. What we learn from the Sun can be applied to similar stars around the galaxy.

By extension, researchers look for Sun-like stars to compare with ours. Even though these stars appear too small for astronomers to distinguish individual features on their surfaces, fluctuations in their light reveal magnetic cycles like those we see on the Sun. In addition, researchers identify Sun-like stars at earlier or later stages in their life, to understand how the young Sun was and how the old Sun will be in the far future.

Many scientists are also interested in using information from the Solar System to find Earth-like planets elsewhere in the galaxy. One complication in this research is that light from stars fluctuates, both due to stellar “weather” and simply as the stars spin. These variations can mimic or mask the signal from exoplanets. For that reason, researchers monitor the Sun’s magnetic fluctuations, as well its light variations on the relatively short periods of time important for exoplanet detection.