The discovery of hypnotic rhythms pulsating from an enigmatic group of stars is music to astronomers.
Key points:
- Many stars pulsate to a regular rhythm but the "music" of delta Scuti stars has been impossible to decipher until now
- Pulsations occur as gas in a star expands and contracts
- Detecting the rhythm of stars can not only help us understand what is happening inside these stars but help us search for planets
Delta Scuti stars, which are about twice as bright and hot as our Sun, are very common in the cosmos.
While many types of stars pulsate in harmony, this is the first time this has been detected in delta Scuti stars, said Tim Bedding, an astronomer at the University of Sydney.
"They can play many notes simultaneously and there are all different types of pulsations."
As gas in a star expands and contracts, the star pulsates, which produces oscillating waves similar to the soundwaves created by musical instruments.
While the beats of "well behaved" stars such as our Sun have regular rhythm and harmony, until now the pulsations of delta Scutis had only ever been a jumbled cacophony of noise.
"It would be like a cat walking on a piano just playing random notes with no method to them.
"But we've found some of these stars do have nice chords, not all of them, but a small fraction," Professor Bedding said.
Tuning into the rhythm of bright young stars
The international team of astronomers led by Professor Bedding identified 60 stars from light curve data collected by NASA's Transiting Exoplanet Survey Satellite (TESS) they report in the journal Nature.
This data enabled them to study regular changes in brightness in the group of stars.
The 'sound' you hear in this video is a simulation of the light wavelengths they detected in one of the stars known as HD 3190 across a 24-hour period condensed into 33 seconds.
The findings indicate the pulsation pattern becomes more complicated as delta Scuti stars get older.
Those with regular beats are just toddlers that have only been burning hydrogen for a few hundred million years.
"That sounds like a long time but in the scheme of a star is actually quite short when you remember the Sun is 4.5 billion years old," Professor Bedding said.
Many of these stars are so young they still hang out in groups.
"They haven't got the hang of social distancing yet.
"We think that a lot of stars form from big clouds of gas in groups and as time goes by they gradually disperse."
But why does this group of younger delta Scuti stars harmonise while others appear to play their own tune?
It could all come down to perspective.
Unlike our Sun, which takes about a month to rotate, delta Scuti stars spin very fast, completing a rotation about every 24 hours.
That means they are a bit squashed or egg-shaped, which may affect our view of them.
The stars that have the nicest pulsation patterns appear to be ones where the poles are pointing towards us.
"Stars in space are oriented randomly so it's just a matter of luck which ones happen to be looking in that direction," Professor Bedding said.
Understanding stars means understanding planets
This discovery opens up a whole new set of stars we can learn about, commented Rob Wittenmeyer, a planetary astronomer at the University of Southern Queensland who was not involved in the discovery.
"We still don't understand how stars work," Professor Wittenmeyer said.
"We kind of know how the Sun works because its right there, but there's a lot we don't know about stars that are different from our Sun."
Studying trembling and pulsating stars — a branch of science known as asteroseismology — can help astronomers understand more about the internal temperatures, structure and chemical composition of stars.
It's the only way we can work out what's going on inside, said Rob Wittenmeyer, who is heading up a new observatory at Mount Kent near Toowoomba called SONG to study pulsating stars.
"It's the same way geologists use earthquakes to probe the inside of the Earth to understand its structure."
From these measurements we can glean a much more accurate idea about the age and mass of the star.
And that's important, if like Professor Wittenmeyer, you are looking for planets.
"If there's a star that has a planet and you can get some seismology on that star, that's gold."
No comments:
Post a Comment