Scientific Programs and Opportunities

Stellar Structure

1Stellar Interior

"Another new field of astronomy to come of age during the 1980s has been the discipline of helioseismology, or studying the internal structure of the Sun by measuring its modes of oscillation. Solar oscillations of about a five minute period probe a wide range of different depths into the Sun and have enabled its detailed internal structure to be defined with quite remarkable precision. For example, the variation of the speed of sound with radius is now known to better than 1% throughout the Sun. These studies can be extended to nearby stars using the 8-meter telescopes with very high resolution spectrographs. For the first time, it will be possible to infer directly the internal structures of stars other than our own Sun."

-Dr. Malcolm S. Longair, Chair of the Gemini Board 1994-1995

What is the internal structure of the stars? The characteristics of the sound waves trapped within the photosphere of a star are critically constrained by the star's physical structure, with the many different waves causing a complex oscillation of the visible surface. The "five minute" oscillations of the Sun have set important limits to the size and structure of its photosphere and internal rate of rotation. The velocity amplitudes associated with the oscillations are subtle, less than 1 m/s, non-repetitive, and they must be monitored for many hours. With Gemini's light gathering power and a spectrograph of sufficiently high resolution, it will now be possible to probe the interiors of nearby main sequence stars in an analogous fashion to the Sun.

Image Credits: 1:NOAO

Ruth A. Kneale / / February 27, 1998