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Cambridge University Science Magazine

The 11-year solar cycle has long been monitored via sound waves, whose emission is related to surficial areas of intense magnetic activity (sun spots). Similar phenomena have been observed in distant stars before, but this is the first time they have been characterised using the new technique of stellar seismology.

Physicists based in Colorado, France and Spain studied data from HD49933, a star lying 100 light years from Earth in the constellation Monoceros (the Unicorn). They found that, like the Sun, the pitch and volume of its song changed in a very specific pattern.

"Essentially, the star is ringing like a bell," said Travis Metcalf, co-author of the study published in Science this month.

The team now plan to probe more stars using the same method, to investigate how and why their sonic patterns vary. For example, HD49933 has a much shorter cycle that the Sun - is this because it is bigger and hotter?

There are wider aims, too. A star's magnetic field influences the climate of any planets within its sphere, and so controls where life can develop. On a more immediate level, understanding these processes should lead to better predictions (and mitigation) of the geomagnetic storms that disrupt our power and communication networks.

Written by Jo Smith