Simulating stars’ sounds to reveal their secrets
In the video above, NASA heliophysicist Alex Young explains how – although sound can’t travel through the vacuum of space, and thus we can’t actually hear the sun or other stars – astronomers have learned to use the vibrations moving through stars to simulate star sounds. The vibrations are powered by the same powerful thermonuclear furnaces in stars’ interiors that enable them to shine. The vibrations appear to earthly astronomers as fluctuations in brightness or temperature on a star’s surface. Jacqueline Goldstein and a team of astronomers from University of Wisconsin-Madison said in late April 2019 that they’ve successfully developed a software program called GYRE that can simulate the complex vibrations that stars produce. A statement about her work, released in late April 2019, explained:
Understand these vibrations, and we can learn more about the inner structure of the star that is otherwise hidden from view.
GYRE plugs into another program called MESA, which facilitates the simulation of stars. The astronomers’ statement explained:
Using this software, Goldstein constructs models of various kinds of stars to see what their vibrations might look like to astronomers. Then she checks how closely simulation and reality match.
Since I made my stars, I know what I put inside of them. So when I compare my predicted vibration patterns against observed vibration patterns, if they’re the same, then great, the inside of my stars are like the insides of those real stars. If they’re different, which is usually the case, that gives us information that we need to improve our simulations and test again.
In particular, she studies large stars, and, she said:
These are the ones that explode and make black holes and neutron stars and all the heavy elements in the universe that form planets and, essentially, new life. We want to understand how they work and how they affect the evolution of the universe. So these really are big questions.
Both GYRE and MESA are open source programs, which means that scientists can freely access and modify the code. Each year, some 40 to 50 people attend a MESA summer school at the University of California, Santa Barbara, to learn how to use the program and brainstorm improvements. Goldstein and her group benefit from all these users suggesting changes to and fixing errors in both MESA and their own program.
They also get a boost from another group of scientists — planet hunters. Two things can make a star’s brightness fluctuate: internal vibrations or a planet passing in front of the star. As the search for exoplanets — planets that orbit stars other than our own — has ramped up, Goldstein has gained access to a trove of new data on stellar fluctuations that are caught up in the same surveys of distant stars.
The latest exoplanet hunter is a telescope named TESS, which launched into orbit last year to survey 200,000 of the brightest, closest stars. Goldstein said:
What TESS is doing is looking at the entire sky. So we’re going to be able to say for all the stars we can see in our neighborhood whether or not they’re pulsating. If they are, we’ll be able to study their pulsations to learn about what’s happening beneath the surface.
Goldstein is now developing a new version of GYRE to take advantage of the TESS data. With it, she’ll start to simulate this stellar orchestra hundreds of thousands strong.
Bottom line: Jacqueline Goldstein and a team of astronomers from University of Wisconsin-Madison said in late April 2019 that they’ve successfully developed a software program called GYRE that can simulate the complex vibrations that stars produce.