Astronomers find 'regular rhythms' coming from distant stars using Nasa space telescope

Andrew Griffin
Wednesday 13 May 2020 16:51
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Astronomers find 'regular rhythms' coming from distant stars using NASA space telescope

Astronomers have found "repeating rhythms" coming from distant stars, in what is being hailed as a major breakthrough.

The research, using data taken from Nasa's Transiting Exoplanet Survey Satellite space telescope, could "revolutionise" the way that scientists can understand the ages, sizes and compositions of a specific class of stars, the researchers say.

"Previously we were finding too many jumbled up notes to understand these pulsating stars properly," said lead author Professor Tim Bedding from the University of Sydney in a statement. "It was a mess, like listening to a cat walking on a piano."

Instead, by using the data from Nasa, team was able to make sense of those pulsations, with the help of brightness measurements of thousands of stars.

"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 said.

The new findings will allow scientists to understand the stars using a technique called astroseismology. Just as scientists can learn more about the inside of the Earth from tracking the reverberations from earthquakes, scientists are able to use similar principles to study the inside of stars by watching their pulsations.

The stars in question are known as delta Scuti stars, and are named after the first of them to be found, a star that is visible from Earth in the constellation Scutum. They are roughly 1.5 to 2.5 times the mass of our Sun.

Researchers had detected a huge number of pulsations from the thousands of those stars they have discovered. But the pulsations seemed to have no discernable rhythm or pattern, making them unable to learn further information about them.

Now in the new research, published in Nature, scientists were able to pick up regularly pulsations from 60 of the stars, which were between 60 and 1400 light years away. Those are thought to be younger stars, meaning that their pulsations happen more rapidly – as they age, the frequency of the pulsations slows and they become jumbled with other signals.

"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," said Professor Bedding.

The main job of Nasa's TESS telescope is not to directly observe stars at all, but rather to watch for when exoplanets may be passing in front of them. But it also takes regular images of the stars themselves, and it was in those pictures that the scientists could spot regular changes in the delta Scuti stars.

The data from the telescope allowed them to gather a large enough dataset on the stars to watch their quick changes, over a long time. That allowed them to isolate the "well-behaved" examples, and conduct further follow-up observations using ground-based telescopes.

"This really is a breakthrough. Now we have a regular series of pulsations for these stars that we can understand and compare with models," said co-author Simon Murphy, a postdoctoral researcher at the University of Sydney.

"It's going to allow us to measure these stars using asteroseismology in a way that we've never been able to do. But it's also shown us that this is just a stepping-stone in our understanding of Delta Scuti stars."

Astronomers have already used the findings to settle debate about the age of one recently-discovered star known as HD31901, which is part of a stream of stars that orbit within our galaxy. Some researchers suggested that the stream was about a billion years old, while others said it formed only 120 million years ago – and the new data suggests the younger age is correct.

"Delta Scuti stars have been frustrating targets because of their complicated oscillations, so this is a very exciting discovery," said Sarbani Basu, a professor of astronomy at Yale University in New Haven, Connecticut, who studies asteroseismology but was not involved in the study.

"Being able to find simple patterns and identify the modes of oscillation is game changing. Since this subset of stars allows normal seismic analyses, we will finally be able to characterize them properly."

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