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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.

Our Work

Center for Astrophysics | Harvard & Smithsonian astronomers look for connections between the Sun and the stars in many ways:

  • Identifying stars that are similar to the Sun at other stages of life. Since the Sun is a fairly typical star, astronomers can construct models for its past and future using similar stars. This research is important for understanding how the Sun enables life as we know it on Earth, and seeing if similar environments exist in other star systems.
    Young Sun-like Star Shows a Magnetic Field Was Critical for Life on the Early Earth

  • Studying magnetic storms on other stars, and applying that knowledge back to the Sun. Younger stars spin faster and have more magnetic activity than older stars. Observing these stars helps us understand the “solar dynamo”: how the Sun generates its magnetic field, and how that generation has changed over the Sun’s lifetime.
    Magnetic Fields on Solar-Type Stars

  • And studying the magnetic field of the Sun to learn about other stars. Using data from the Sun, researchers create three-dimensional models of magnetic field generation, which can be tested against observational data from other stars. The end goal is understanding exactly how stellar magnetic fields are created, and how they influence planets in their systems.
    The Secret of Magnetic Cycles in Stars

  • Measuring the gravitational tug of planets on the Sun, in hopes of finding exoplanets the size of Earth. To do this, astronomers track the Doppler effect: the shift in color of the Sun’s light as planets pull it very slightly. Researchers have detected a number of large exoplanets using this technique, but to find smaller Earth-size planets, they need much more accurate data. For that reason, astronomers looked at our own Sun for the wobble produced by Venus, which is very close in mass to Earth, but closer to the Sun.
    Rediscovering Venus to Find Faraway Earths

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.