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Starquakes: Listen to the Sounds of Stars!

Starquakes are tantamount to earthquakes: they help us understand the interior of stars. Thanks to a new study published in the journal Nature Astronomy, you can also hear a ringing sound coming from the insides of a group of stars!

Spinning stars.

A starquake is an astrophysical occurrence whereby the crust of a neutron star is suddenly adjusted. This movement causes internal sound waves which result in the star ringing. The scientists of the new study have used these sounds to gain a deeper understanding of the birth of stars 8 billion years ago. This forms part of a greater field of study called asteroseismology—investigating the different types of oscillations in stars provides invaluable information about the internal structure of stars.

The team behind the new findings took to this branch of asteroseismology, examining starquakes, to calculate the orientation of the angle of spin of a group of 48 red giant stars existing in our galaxy, the Milky Way. Study author, Dr Dennis Stello, likens starquakes to earthquakes: the former are used to analyse the interior of stars just like seismologists use the latter to collect data about Earth’s interior. This approach promises to go back in time: according to Stello, it can help us understand the processes that took place billions of years ago, back when the universe was still very young.

These stars come from 2 ancient clusters of stars, one over 2 billion years of age, and the other exceeding 8 billion years.

“The benefit of studying ancient star clusters is that the interfering dust and gas has gone, yet the stars still preserve the signature of the initial conditions in the cloud where they were born,” says Dr Stello.

Stars are born in clusters, generated from the collapse of huge clouds of gas and dust—a violent process resulting in thousands of stars per cluster. At this moment in time, astronomers cannot quite study these star nurseries because of interference from the gas and dust. Therefore, to avoid these difficulties, the team chose to focus on red giant stars that were ancient.

The results that the majority of these stars would spin in such a way that they were aligned with each other. This constitutes a surprising result, points out Dr Stello, who explains that previous assumptions had ruled out this alignment because it was thought that the rotational energy of the ‘birthplace’ of stars (the huge clouds of gas and dust) would have been scrambled by great turbulence.

“Our finding that the spins of about 70 per cent of the stars in each cluster are strongly aligned, and not randomly orientated as was expected, tells us that the angular momentum of the gas and dust cloud was efficiently transferred to the new stars,” says Dr Stello.

And, you know what’s even more awesome of what has come out of this study?! We can listen to the ringing sounds of different stars!


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