There's a harmonic heartbeat among pulsating stars.
Listening to the ‘beats’ of the nuclei of the stars, astronomers have identified for the first time a regular rhythm for pulsating stars, a class of objects that until now had baffled scientists.
“Previously we were finding too many confusing notes to understand these pulsating stars,” lead author Professor Tim Bedding of the University of Sydney said in a statement. “It was a disaster, like listening to a cat walking on a piano.”
An international team used data from NASA’s TESS mission, a space telescope used primarily to detect planets around some of the closest stars to Earth, to try and better understand one of the many cosmic mysteries. It provided scientists with brightness measurements of thousands of stars, allowing them to find 60 whose pulses made sense. Their findings are reported in Nature.
“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,” Professor Bedding revealed.
The recent discoveries turned out to be an important contribution to our overall understanding of what goes on within the countless trillions of stars across the universe. The intermediate-sized stars in question, approximately 1.5 to 2.5 times the mass of our Sun, are known as Scuti delta stars, which are named after a variable star in the constellation Scutum.
By studying the pulsations of this class of stars, astronomers had previously identified many pulsations but were unable to resolve any clear pattern. The Australian-led team of astronomers has announced detecting remarkably regular high-frequency pulse modes in 60 delta Scuti stars, ranging from 60 to 1,400 light-years away.
“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,” added Professor Bedding.
The heartbeat of a star
But in order to use TESS to study the pulsating stars, researchers needed to come up with a software that would work, and Daniel Hey, a Ph.D. student at the University of Sydney and co-author on the paper did precisely that.
“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,” Hey said.
“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 interior of stars was once a mystery to science. But in recent decades, astronomers have been able to detect the internal oscillations of stars, revealing their interior 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 that allow us to observe the heart of the massive nuclear furnaces that power the universe.
This branch of science, known as asteroseismology, allows us not only to understand how distant stars work, but to understand how our own Sun produces sunspots, eruptions, and deep structural movements. Applied to the Sun, it provides very precise information about its temperature, chemical composition, and even neutrino production, which could be important in our search for dark matter.
“Asteroseismology is a powerful tool by which we can understand a broad range of stars,” Professor Bedding explained.
“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.”
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