Their findings are published in the journal Nature. Lead author Professor Tim Bedding, from the University of Sydney, said:
“Previously we were finding too many jumbled up notes to understand these pulsating stars properly. It was a mess, like listening to a cat walking on a piano.”
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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:
“The incredibly precise data from NASA’s TESS mission have allowed us to cut through the noise. Now we can detect structure, more like listening to nice chords being played on the piano.”
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 stars 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 of stars, astronomers had previously detected many pulsations, but had been unable to determine any clear patterns.
“This definitive identification of pulsation modes opens up a new way by which we can determine the masses, ages and internal structures of these stars.”
Daniel Hey, a Ph.D. student at the University of Sydney and co-author on the paper, designed the software that allowed the team to process the TESS data. He said:
“We needed to process all 92,000 light curves, which measure a star’s brightness over time. From here we had to cut through the noise, leaving us with the clear patterns of the 60 stars identified in the study.
“Using the open-source Python library, Lightkurve, we managed to process all of the light curve data on my university desktop computer in a just few days.”
The insides of stars were once a mystery to science. But in the past few decades, astronomers have been able to detect the internal oscillations of stars, 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.
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 production of neutrinos, which could prove important in our hunt for dark matter. Professor Bedding said:
“Asteroseismology is a powerful tool by which we can understand a broad range of stars. This has been done with great success for many classes of pulsators including low-mass sun-like stars, red giants, high-mass stars and white dwarfs. The delta Scuti stars had perplexed us until now.”
Isabel Colman, a co-author and Ph.D. student at the University of Sydney, said:
“I think it’s incredible that we can use techniques like this to look at the insides of stars. Some of the stars in our sample host planets, including beta Pictoris, just 60 light years from Earth and which is visible to the naked eye from Australia. The more we know about stars, the more we learn about their potential effects on their planets.”
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:
“Our results show that this class of stars is very young and some tend to hang around in loose associations. They haven’t got the idea of ‘social distancing’ rules yet.”
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:
“We are thrilled that TESS data is being used by astronomers throughout the world to deepen our knowledge of stellar processes. The findings in this exciting new paper led by Tim Bedding have opened up entirely new horizons for better understanding a whole class of stars.”
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 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.]