Do Stars Remember Their Past? Study Sheds New Light on Old Theories of Stellar Evolution

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First Stages of Young Star

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The younger star within the heart is in a molecular cloud and is enveloped by a disk. In the primary phases of its life, the star attracts quite a few supplies, for instance, by magnetic fields, that are continuously remixed in turbulence. The inside of the younger star is permeated by pulsations. Credit: Mirjana Keser

A star’s “childhood” shapes their stellar evolution. 

From newborns to youngsters, stars of their “young years” pose a major scientific problem. It is extraordinarily difficult to mannequin the method of star formation in theoretical fashions as a result of its complexity. Observing a star’s oscillations is without doubt one of the few strategies to search out out extra a couple of star’s age, construction, or formation.

“Comparable to the exploration of the Earth’s interior with the help of seismology, we can also make statements about their internal structure and thus also about the age of stars based on their oscillations,” says Konstanze Zwintz.

Zwintz is considered a pioneer within the younger area of asteroseismology and heads the analysis group “Stellar Evolution and Asteroseismology” on the Institute for Astro- and Particle Physics on the University of Innsbruck.

Star Evolution Model

The blue line exhibits the evolution of a star earlier than the transition to the principle sequence (blue dot) in response to the classical fashions utilized for the reason that 1950s. The white line represents the life like illustration ensuing from Thomas Steindl’s new mannequin – the star’s “wild” years from infancy to teenage years, with the evolution working from proper to left within the picture. Credit: Thomas Steindl

Because of the elevated potential to make exact observations with house telescopes like TESS, Kepler, and James Webb, the study of star oscillations has evolved considerably in recent years. These advances are also shedding new light on decades-old theories of stellar evolution.

With a new model to zero hour of adult stars

As long as stars are not yet converting hydrogen into helium in their cores, they are referred to as “children.” At this stage, they are in the pre-main sequence; after ignition, they become adults and move on to the main sequence.

“Research on stars has so far focused mainly on adult stars – such as our Sun,” says Thomas Steindl, a member of Konstanze Zwintz’s research group and lead author of the study.

“Even if it sounds counterintuitive at first glance, so far little attention has been paid to the evolution of the pre-main sequence because the phase is very turbulent and difficult to model. It’s only the technological advances of recent years that allow us a closer look at the infancy of stars – and thus at that moment when the star begins to fuse hydrogen into helium.”

In their current study, the two Innsbruck researchers now present a model that can be used to realistically depict the earliest phases of a star’s life long 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 a 2019 meeting, Thomas Steindl spent months refining the method for using this stellar evolution code to recreate the chaotic phase of early star formation and then predict their specific oscillations.

“Our data show that stars on the pre-main sequence take a very chaotic course in their evolution. Despite its complexity, we can now use it in our new theoretical model.” Steindl said.

Thus, the astronomer shows that the way the star is formed has an impact on the oscillation behavior even after ignition of nuclear fusion on the main sequence: “The infancy has an influence on the later pulsations of the star: This sounds very simple, but it was strongly in doubt. The classical theory assumes that the time before ignition is simply irrelevant. This is not true: Comparable to a musical instrument, even subtle differences in the composition lead to significant changes in the tone. Thus, our modern models better describe the oscillations in real stars.”

Konstanze Zwintz is delighted with this discovery and is very optimistic about the future: “I was already convinced about 20 years ago, when I first saw the oscillation of a young star in front of me on the screen, that I would one day be able to prove the significance of early stellar evolution on the ‘adult’ star. Thanks to the great work of Thomas Steindl, we have now succeeded: Definitely a eureka moment for our research group and another milestone for a better understanding of the growth steps of stars.”

Reference: “The imprint of star formation on stellar pulsations” by Thomas Steindl, Konstanze Zwintz and Eduard Vorobyov, 19 September 2022, Nature Communications.
DOI: 10.1038/s41467-022-32882-0