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Figure 3. Three “earth-sized” exoplanets found around the star Kepler-37 compared with solar system planets. Courtesy of NASA.
exoplanet researchers sprang up, starting with two Canadian and French satellite efforts, microvariability and oscillations of stars (MOST) and convection, rotation, and planetary transits (CoRoT), and culminating with NASA’s superbly equipped Ke- pler spacecraft.
The symbiosis between the two fields comes about because, to measure an exoplanet’s size from transit data (where the planet crosses in front of the star), you need to know the star’s size. This would seem hard to get from the “point source” stars we see at our distance, and this is where astero- seismology comes in. The time series data about the stars oscillations that asteroseismology collects also allows one to create a stellar model for each star; stellar structure is a rath- er well-developed field. Such stellar models produce, among many other things, an estimate of the star’s size and age. This directly gives the planet’s size and, moreover, an estimate of its age (about the same as the star’s).
One of the major goals of the Kepler mission, and its modi- fied K2 mission, was to find earthlike exoplanets by looking at smaller stars like the sun. The star Kepler-37, 220 light years away in the constellation Lyra, was one of its nicer suc- cess stories. Three planets roughly comparable to Earth in size (see Figure 3) were found orbiting a star with a diameter 77% that of the sun (measured to an astounding 4% accu- racy!). Finding out if these planets are suitable for life is a larger, further story, but asteroseismology lets us know the first-order details that get us in the game.
Like any other technique, asteroseismology can produce more information when used in combination with other
techniques. When used in combination with spectroscopic data, it produces stellar masses accurate to about 6% and di- ameters accurate to 2%! This technique has been used on hundreds of smaller and medium-sized stars to date.
When used on larger, red giant stars, asteroseismology has been able to distinguish between two different evolutionary stages of hydrogen and helium burning that could not be separated before and show that the interior core rotated at least 10 times faster than the surface.
And as a final gem, asteroseismology found a new, interest- ing class of stars, now called “heartbeat stars,” which pro- duce brightness time series that look very much like the waveforms found in human electrocardiograms (Matthews, 2015). The reason for this similarity is actually rather simple. Many stars are in binary systems, with orbits that are highly eccentric (pronouncedly elliptical). As the companions draw close together in the perigee part of the orbit, large tides that ring the oscillation modes of the stars once per orbital pe- riod are raised. These modes die out as the stars eventually move apart, flattening the brightness curve back to its un- disturbed state. By monitoring these unique oscillations in both intensity and motion (Doppler), even more informa- tion can be obtained about stellar structure.
Creating Our Universe with Sound:
The Big Bang
At this point in time, it is accepted that our universe was created in a singular event mockingly called (by one of its most famous opponents, Fred Hoyle) “The Big Bang.” This
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