Asteroseismology: Stealing the geoseismologists’ rule book and launching it into space

Astronomers have been trying to update the biography of the Sun for decades, at the same time trying to confirm our models for its internal structure. Like the Earth – of which we can sample directly less than 0.2% of its total depth – most of the interior of the Sun is hidden from direct view.

Except for neutrinos from the solar core, we receive direct information from a surface layer of gas whose depth is only 0.05% of the radius of the Sun.

Astronomers, faced with the same challenge that geophysicists had tackled before us to probe the deep interior of the Earth, turned to the rule book of geoseismology. For the Sun, we could apply the principles of global helioseismology and eventually time-distance seismology, using the intrinsic vibrations of the Sun caused by sound waves propagating in the solar interior.

Much of this was possible with telescopes on the Earth’s surface because of the very high signal-to-noise and surface spatial sampling possible for solar observations. But when it came to extending this technique to the stars, through asteroseismology, it was necessary not to toss out the rule book, but to toss it upwards, into space.

Canada’s first space telescope, called MOST, was one of the pioneers, later joined by the French CoRoT space mission and eventually NASA’s Kepler satellite. These instruments are the most sophisticated stellar lightmeters ever built, and launching them into space launched a revolution in ultraprecise photometry of stars and exoplanets. That in turn launched a revolution in our ability to seismically probe distant stars, and to put our own Sun in better context by studying the interiors of other suns. Not just ‘middle-aged’ suns like our own, but senior suns, and teen suns, and baby suns, and even suns still in the womb.

Even for our own Sun, the seismic data are driving the physics, so we need to include what used to be considered third-order effects lost in the noise, if we’re to match the eigenfrequencies to their current measured accuracies.

Join us on a lunchtime voyage through space and time, where the guide book contains the principles of time series analysis and mathematical inversion, to see how far we have come in only a decade, and the exciting frontiers that are ahead of us.