What is asteroseismology?
Excellent question, probably nobody! Asteroseismology is one of the more niche sub-fields in astronomy, but it's my current research, so it only feels fitting for the maiden voyage of this blog! Let's get into it.
Word breakdown: Astero- (Greek: star, star-like) -Seism (Greek: earthquake, shaking) -ology (Greek: study of)
Given this, we can assume that asteroseismology is the study of the shaking of stars, which is close! Yay, etymology! It is, more accurately, the study of stellar oscillations.
"Stellar oscillations?", I hear you ask. "Ceri, what does that mean?"
It means the stars are singing.
Temperature changes in a star, caused by convection (hot stuff moves up/out, cool stuff moves down/in) create waves that bounce through the star - waves that are mechanically the same as sound waves. Mechanical wave is mechanical wave. These waves cause the star to expand and contract, although this isn't visible to the naked eye, and the sheer amount of waves makes the star all wiggly. These types of stars are called solar-like oscillators, because that's how the Sun works.
Pause to imagine the Sun jiggling around. Pause to give an amused exhale. Aaand post resumed.
These waves, and the temperature changes they are related to, actually cause the star to brighten and dim. You may have been told as a child that stars don't actually twinkle - well, they don't if you're looking from earth, but with space-based telescopes like the Kepler mission and TESS, they absolutely do. And that twinkling is what astronomers are measuring.
Measuring these waves lets us learn about the internal structure of stars with incredible accuracy. I know this from experience - I was the first to perform asteroseismology on two specific red giant stars, and my colleague and I discovered one of them was 60% older than we thought it was. Cool stuff!
But wait, how do the waves tell us how old the star is? That might seem a bit random. Well, they don't tell us directly. The most important values given directly from analysis of these stars are mass and radius. In a red giant star, like the one I was analyzing, the mass is related to its age given how the life cycle of stars works, which I will talk about in another post.
But why are we doing this, anyway?
Asteroseismology gives us an incredibly detailed insight into a star. The reason that's important? Most of the time, it's because we really care about what's around the star. Namely, exoplanets (planets in other star systems.
Calculating stellar parameters is crucial to exoplanet research. Measuring a star's radius allows us to measure the radius of a planet using the transit method (where a planet blocks light from the star), as opposed to simply the ratio, and the star's mass allows us to determine the planet's mass using the radial velocity method, again, as opposed to simply a ratio.
So that's that! Asteroseismology in a nutshell! I hope you learned something, and as always, feel free to ask questions and do your own reading! Ad arcana universi!
REFERENCES/FURTHER READING:
Some lecture notes on asteroseismology
Asteroseismology.org (includes downloadable .wav files where you can listen to stars!!!!!)
