Astronomers Find Regular Rhythms Among Pulsating Stars

A delta Scuti variable star.

Still image from animation showing a simulation of pulsations in the delta Scuti variable star called HD 31901, based on brightness measurements by NASA's Transiting Exoplanet Survey Satellite (TESS). Image: via Dr. Chris Boshuizen (twitter.com / DrChrispyMusic or instagram.com / DrChrispyMusic), with assistance from Dr. Simon Murphy and Prof. Tim Bedding (twitter.com / timbedding)

Through the noise, young stars reveal their inner workings. An Australian-led team has solved the mystery of how some rapidly rotating young stars pulsate. Delta Scuti stars can now be studied in more detail thanks to the work of Professor Tim Bedding and colleagues. By listening to the beating hearts of these, astronomers have identified a rhythm of life for a class of stellar objects that had puzzled scientists until now.

Their findings are published in the journal Nature. Lead author Professor Tim Bedding, from the University of Sydney, said:

The international team used data from NASA’s Transiting Exoplanet Survey Satellite (TESS), a space telescope mainly used to detect planets around some of the nearest stars to Earth. It provided the team with brightness measurements of thousands of stars, allowing them to find 60 whose pulsations made sense. Professor Bedding said:

Delta Scuti stars

The findings are an important contribution to our overall understanding of what goes on inside the countless trillions of stars across the cosmos. The intermediate-sized ones in question – about 1.5 to 2.5 times the mass of our Sun – are known as delta Scuti stars, named after a variable star in the constellation Scutum. When studying the pulsations of this class, astronomers had previously detected many pulsations, but had been unable to determine any clear patterns.

 The Australian-led team of astronomers has reported the detection of remarkably regular high-frequency pulsation modes in 60 delta Scuti stars, ranging from 60 to 1400 light-years away. Professor Bedding said:

Daniel Hey, a Ph.D. student at the University of Sydney and co-author of the paper, designed the software that allowed the team to process the TESS data. He said:

Asteroseismology

The insides of stars were once a mystery to science. But in the past few decades, astronomers have been able to detect their internal oscillations, revealing their structure. They do this by studying stellar pulsations using precise measurements of changes in light output. Over periods of time, variations in the data reveal intricate — and often regular — patterns, allowing us to stare into the very heart of the massive nuclear furnaces that power the universe.

Professor Tim Bedding studies stars throiugh the discipline of asteroseismology.
Professor Tim Bedding. (Image: University of Sydney)

This branch of science, known as asteroseismology, allows us to not only understand the workings of distant stars, but to fathom how our own Sun produces sunspots, flares, and deep structural movement. Applied to the Sun, it gives highly accurate information about its temperature, chemical make-up, and even the production of neutrinos, which could prove important in our hunt for dark matter. Professor Bedding said:

Isabel Colman, a co-author and Ph.D. student at the University of Sydney, said:

Poor ‘social distancing’

The identification of regular patterns in these intermediate-mass stars will expand the reach of asteroseismology to new frontiers, Professor Bedding said. For example, it will allow us to determine the ages of young moving groups, clusters, and stellar streams, adding:

Dr. George Ricker, from the MIT Kavli Institute for Astrophysics and Space Research, the Principal Investigator for NASA’s Transiting Exoplanet Sky Survey, from which the study took its data, said:

Watch the pulsations of a Delta Scuti star! In this illustration, the star changes in brightness when internal sound waves at different frequencies cause parts of the star to expand and contract. In one pattern, the whole star expands and contracts, while in a second, opposite hemispheres swell and shrink out of sync. In reality, a single star exhibits many pulsation patterns that can tell astronomers about its age, composition, and internal structure.

The exact light variations astronomers observe also depend on how the star’s spin axis angles toward us. Delta Scuti stars spin so rapidly that they flatten into ovals, which jumbles these signals and makes them harder to decode. Now, thanks to NASA’s Transiting Exoplanet Survey Satellite, astronomers are deciphering some of them. (Image: NASA’s Goddard Space Flight Center)

Provided by: University of Sydney [Note: Materials may be edited for content and length.]

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