Stellar childhood shapes stellar evolution – ScienceDaily

In classical models of stellar evolution, little importance has yet been given to the early evolution of stars. Scientists are now showing that star biography is already forming through its early stages.

From kids to teens: the stars in their “younger years” present a major challenge to science. The process of star formation is particularly complex and difficult to determine in theoretical models. One of the few ways to learn more about a star’s composition, structure, or age is by observing its vibrations. “Compared with the exploration of the Earth’s interior with the help of seismology, we can also make statements about its internal structure, and thus also about the age of stars based on their oscillations,” says Konstanze Zwintz. The astronomer is a pioneer in the field of young stellar mercury science and leads the research group “Stellar Evolution and Stellar Seismology” at the Institute for Astrophysics and Particles at the University of Innsbruck. The study of stellar oscillations has developed greatly in recent years because the possibilities of accurate observation through telescopes in space such as TESS, Kepler and James Webb have improved on several levels. These developments are now also shedding new light on decades-old theories of stellar evolution.

With a new zero hour model of adult stars

Stars are called “children” as long as they have not yet burned hydrogen to helium in their cores. At this point, they are in the pre-major sequence; After ignition, they become adults and move to the main sequence. “Research on stars so far has mainly focused on adult stars – such as our Sun,” says Thomas Steindl, a member of the Konstanz Zwentz research group and lead author of the study. “Even if it seems counterintuitive at first glance, so far not much attention has been paid to the evolution of the pre-core sequence because the phase is very turbulent and difficult to model. Only technological developments in recent years allow us to approximate to look at the beginning of the stars – and therefore at that moment in which the star begins to fuse hydrogen into helium.” In their current study, the researchers at Innsbruck now present a model that can be used to realistically depict the early stages of a star’s life before they become adults. The model is based on the open source stellar evolution program MESA (Modules for Experiments in Stellar Astrophysics).

Inspired by a talk given by astronomer Eduard Vorobyov of the University of Vienna at the 2019 meeting, Thomas Steindl spent months refining the way he used this stellar evolution code to recreate the chaotic phase of early star formation and then predict their specific oscillations. “Our data shows that stars in the pre-main sequence take a very chaotic path in their evolution. Despite their complexity, we can now use them in our new theoretical model.” Steindl said. Thus, the astronomer explains that the way a star forms has an effect on the oscillation behavior even after nuclear fusion ignites in the main sequence: “Childhood has an effect on the subsequent pulsations of the star: this seems very simple, but there was great doubt. Classical theory assumes that the time during which Preceding ignition is simply irrelevant. This is not true: compared to a musical instrument, even minute differences in composition lead to significant changes in tone. Thus, our modern models best describe oscillations in real stars.”

Konstanze Zwintz is pleased with this discovery and is very optimistic about the future: “I was already convinced about 20 years ago, when I first saw a young star vibrate in front of me on the screen, that I would one day be able to prove the importance of early stellar evolution on an “adult” star.” Thanks to the wonderful work of Thomas Steindl, we are now successful: definitely an eureka moment for our research group and another milestone for a better understanding of the steps of star growth.”

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Materials Introduction of University of Innsbruck. Note: Content can be modified according to style and length.