The childhood of stars shapes the evolution of stars

Tarantula Nebula: In this famous star-forming region of our neighboring galaxy, the Large Magellanic Cloud, many young stars are still in their molecular clouds. Credit: James Webb Space Telescope

In classical models of stellar evolution, little importance has yet been given to the early evolution of stars. Now Thomas Steindl of the Department of Astrophysics and Particles at the University of Innsbruck shows for the first time that star biography has already formed in its early stage. The study was published in Nature Communications.

From kids to teens, stars in their “young years” present a major challenge to science. The star formation process is particularly complex and difficult to define 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 exploring the interior of the Earth with the help of seismology, we can also release data about its internal structure, and therefore also about the age of stars based on their oscillations,” Konstanze Zwintz says.

The astronomer is a pioneer in the field of young interstellar mercury and leads the research group Stellar Evolution and Asteroseismology 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 now also shed new light on decades-old stellar theories has evolved.

Astrophysics: stellar childhood shapes the evolution of stars

The young star in the center is in a molecular cloud and encased in a disk. In the early stages of its life, the star attracts many substances, for example, through magnetic fields, which are constantly remixed in turbulence. The inner pulsations of the young star permeate. Credit: Mirjana Ksir

A new model for the zero hour 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 has so far 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, little attention has yet been paid to the evolution of the pre-primary sequence because the stage is very turbulent and difficult to model. Only technological advances in recent years allow us to approximate to look at the origins of stars – and thus at that moment in which the star begins to fuse hydrogen into helium.”

Astrophysics: stellar childhood shapes the evolution of stars

The blue line shows the star’s evolution before the transition to the main sequence (the blue dot) according to classical models applied since the 1950s. The white line is the realistic representation resulting from Thomas Steindl’s new model – the star’s “wild” years from childhood to teenage years, with development running from right to left in the image. Credit: University of Innsbruck

In their current study, the two researchers in 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 is formed has an effect on wiggle Behavior even after nuclear fusion ignites in the main sequence: “Childhood has an effect on the star’s late pulsations: this seems very simple, but it has been highly questionable. The classical theory assumes that the time before ignition is simply irrelevant. .This is not true: it can be compared to Musical instrumentEven slight differences in composition lead to significant changes in tone. Thus, our recent models better describe oscillations in real stars. “

Konstanze Zwintz says, “I was already convinced about 20 years ago, when I first saw a young star vibrate in front of me on screen, that I would one day be able to prove the importance of early stellar evolution on an ‘adult star. Thanks to the remarkable 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. ”


Bypassing the nucleus is limited by the absence of a solar convective nucleus and some Sun-like stars


more information:
Thomas Steindl et al, Imprint of star formation on stellar pulsations, Nature Communications (2022). DOI: 10.1038 / s41467-022-32882-0

Introduction of
University of Innsbruck


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