Science: Satellite Data Sheds New Light on the Sun and Nearby Stars

Illustration of the CoRoT satellite.

Image © CNES/illustration David Ducros

Some of the first data collected by the CoRoT space telescope mission, launched in December 2006, provides valuable information about the physical vibrations and surface characteristics of nearby stars that are similar to the Sun, researchers say. This novel information illustrates the great value of space-based observations and provides astronomers with insights into the interior of the Sun, other stars, and the evolution of our galaxy.

Writing in the 24 October issue of Science, Eric Michel from the Observatory of Paris, the Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA), and the Centre National de la Recherche Scientifique (CNRS) joined with a large group of colleagues from across Europe and South America to analyze the data from CoRoT (Convection, Rotation and Planetary Transits). They determined that three nearby stars, all significantly hotter than the Sun, also have larger vibrations, or oscillations, and much finer surface texture, or granulation.

With this unprecedented data, the researchers show that the stars' oscillations are about 1.5 times as vigorous as the Sun's, and their granulation is about three times finer. The observed oscillations, though much more intense than the Sun's, are still about 25% weaker than most models predicted.

These landmark results represent the first time researchers have been able to accurately gauge the oscillation amplitudes and granulation signatures of solar bodies in our universe, other than the Sun.

The initial discovery of oscillations in our Sun in the late 1970s led to the creation of "solar seismology," which has since been used to measure the movement and transport of heat around the Sun. Solar seismology led to rapid progress in understanding the Sun's internal structure, but eventually researchers hit a wall. Accurate measurements of solar-like oscillations require the collection of precise data from long, uninterrupted sequences of observations, making ground-based study impossible.

"Although the energy from the Sun is more or less constant over our lifetimes, even very small variability in its output can have important effects," said Brooks Hanson, deputy editor for physical sciences at Science. "Understanding that small variability is critical, for example, in predicting solar storms and space weather, and for resolving the causes of changes in Earth's climate... These observations [by Michel and colleagues], and more in the future, will provide the essential data for improving our understanding of the interior of the Sun, and stars in general."

The findings presented by Michel and colleagues are based on light curves obtained with the CoRoT satellite over a period of 60 days, and help to refine our understanding of stars and the Sun. These results "allow us to place our Sun within the bigger picture of the evolution of our galaxy and the local universe," says Ian Osborne, senior editor of Science.

A press conference related to the Science paper was in Paris on Wednesday 22 October. Speakers included Michel, Annie Baglin and Michel Auvergne from the Observatory of Paris-LESIA-CNRS and Richard Bonneville from the Centre National des Etudes Spatiales.

Brandon Bryn

23 October 2008