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Astrophysicists simulate the sounds of stars to reveal their secrets



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Sound may not be able to stream through the vacuum of space.

But that does not prevent Sterne from unleashing a symphony of subsonic notes, as their hearth furnaces create complex vibrations. Telescopes can detect these oscillations as variations in brightness or temperature on the surface of a star.

Understanding these vibrations allows us to learn more about the inner structure of the star, which is otherwise invisible.

"A cello sounds like a cello because of its size and shape," says Jacqueline Goldstein, a student at the Department of Astronomy at the University of Wisconsin-Madison. "The vibrations of stars also depend on their size and structure."

In her work, Goldstein explores the connection between star structure and vibration by developing software that simulates different stars and their frequencies. By comparing her simulations to real stars, Goldstein can refine and enhance her model as astrophysicists search her beneath the surface of stars, surveying her subtle tones.

With frequencies that repeat on the order of minutes to days, you would have to accelerate these stellar vibrations a thousand or a million times to bring them into the realm of human hearing. This reverberation can most likely be called a starquake after their seismic cousins ​​on Earth. The study area is called Astroseismologie.


As stars merge hydrogen with heavier elements in their nuclei, hot plasma gas vibrates and makes stars flicker. These variations can inform researchers about the structure of a star and how it will change with the age of the star. Goldstein explores stars larger than our own sun.

"Those are the ones that explode, forming black holes and neutron stars, and all the heavy elements in the universe that make up planets and essentially new lives," says Goldstein. "We want to understand how they work and how they affect the evolution of the universe, so those really big questions."

In collaboration with the astronomy professors Rich Townsend and Ellen Zweibel Goldstein developed a program called GYRE, which follows the star. Simulation program MESA. With this software, Goldstein constructs models of different types of stars to see how their vibrations might look to astronomers. Then she examines how exactly simulation and reality fit together.

"Since I made my stars, I know what I put into them, so when I compare my predicted vibrational patterns to observed vibrational patterns, they are the same great, the inside of my stars is like the inside of those real stars. If they are different, which is usually the case, we get the information we need to improve and retest our simulations, "says Goldstein.

Both GYRE and MESA are open source programs. This means scientists can freely access and modify the code. Each year, around 40 to 50 people attend a MESA summer school at the University of California, Santa Barbara to learn how to use the program and make improvements in brainstorming. Goldstein and her group benefit from all those users who propose changes to MESA and their own program and fix bugs.

You also get a boost from another group of scientists – planet hunters. Two things can cause the brightness of a star to fluctuate: internal vibrations or a planet passing in front of the star. As the search for exoplanets – planets orbiting other stars than our own – has increased, Goldstein has gained access to a wealth of new data on stellar fluctuations that have been trapped in the same distant star examinations.

The newest exoplanet Hunter is a telescope called TESS, launched into orbit last year to survey 200,000 of the brightest, closest stars.

"What TESS does is the whole sky," says Goldstein. "So we'll be able to tell if all the stars we see in our neighborhoods are pulsing or not, and if they do, we can study their pulsations to see what's below the surface happens. "

Goldstein is now developing a new version of GYRE to use the TESS data. With that she begins to simulate this star orchestra by the hundreds of thousands.

With these simulations, we may be able to learn a little more about our cosmic neighbors just by listening.


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Provided by
University of Wisconsin-Madison




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Astrophysicists Simulate the Sounds of Stars to Unveil Their Secrets (2019, April 27)
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