When Lisa Pugnet looks at the stars, she looks at her computer screen at the Institute of Science and Technology (ISTA) in Klosterneuburg (Dallen district). On the screen she sees data and images from the Kepler and TES space telescopes, which regularly provide NASA with new images of stars in the Milky Way. The 29-year-old astrophysicist is considered Austria's youngest professor and a proven expert on what and, above all, how the stars in our galaxy shine.
However, the twinkling stars you see from Earth are mostly due to Earth's atmosphere. Wind and temperature changes reflect light and create rapid light changes. But: “Even if you ignore the atmospheric effects, you can still see the stars shining,” Pugnet explains. Images from space telescopes confirm the effect. “This is due to ongoing processes on the surface and inside the star.”
Starlight full of secrets
Starquake: The entire star shakes
Stars, like our Sun, contain a hot cloud of gas called plasma. The plasma is constantly in motion, “like a cooking pot,” Pugnet describes it. The released energy creates earthquakes on the star's surface, which cause the star's surface to vibrate, and these lead to an amazing physical phenomenon: “All the tiny gas movements trigger sound, and this sound propagates through the star's interior and the whole star vibrates,” it explains. Bucknet.
As a result, the star constantly rises and falls and the star oscillates. As the star contracts, the surface is closer to the hot center, the surface becomes hotter, and the star shines brighter. Conversely, as the star expands, the surface cools and the surface becomes faintly luminous.
Looking into space is a glimpse into the future
“A small star oscillates much faster than a large star,” explains Pagnet. Massive stars glow more slowly because sound takes longer to travel through the star. Massive stars are also often older and more massive.
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By depending on the frequency with which the stars flash, Buknett and his team at ISTA can make inferences about the star's mass, radius, composition and age. For the astrophysicists at ISTA, they are a glimpse into the future: older stars predicting what our younger Sun will become. “If we understand what goes on inside ancient stars, we can understand how our Sun formed,” says Bucknett.