# Animations of a pulsating star

## 2. Movie animations of stars pulsating in radial and non-radial modes

This animation of a radial pulsation was produced by Beau Bellamy as part of an Honours project in the School of Physics at the University of Sydney. The star is pulsating simulatenously in two radial modes with a ratio of 1.75.

These animations were produced by students Alexandra Chambers and Darran Baker as part of a course on Scientific Computing in the School of Physics at the University of Sydney.

 l=1 m=0 l=1 m=1 l=2 m=1 l=2 m=2

 l=3 m=0 l=3 m=1 l=3 m=2 l=3 m=3

More animations in a different colour scheme were made by Chris Ormerod (undergraduate physics student).

More animations of pulsating stars, including radial pulsations, by Zoltan Kollath (Konkoly Observatory, Hungary)

Each animation shows a different mode of pulsation, with the amplitudes greatly exaggerated. A real star, like the Sun, will pulsate simultaneously in all these modes and each will have a slightly different period. In the Sun, the pulsation modes have periods in the range 4 to 8 minutes. Each mode is a sound wave, and the period of each one gives information about the sound speed in that part of the star where the sound wave spends most of its time. Combining the periods of all modes allows us to build an accurate picture of the sound speed inside the whole star, and hence infer crucial details about its internal temperature, rotation and composition.

For example, during its life a star burns hydrogen into helium in its core. The speed of sound in helium is less than in hydrogen, so the pulsation periods of a star increase as it gets older (its voice deepens!). Thus, measuring pulsations and comparing with theory allows us to measure the ages of stars.

Last updated 20-Dec-2005 by Tim Bedding