Experts find new ways of charting the rise of original singing stars

Published on Saturday 12 August 2006 01:54

THEY may not be your conventional pop stars, but those pinholes in the curtain of night can sing, according to a leading astronomer.

To prove their theory, astronomers had to compensate for the vacuum of space. They measured the vibrations induced by sound waves produced deep within stars, including the Sun. The use of ultrasound techniques enabled them to calculate precisely the composition, density and temperature of a star.

"Stars have natural vibrations that are sound waves, just as musical instruments do," says astronomer and astrophysicist Professor Don Kurtz.

"For the star, the vibrations start by changes in the passage of energy from the nuclear inferno in the heart of the star on its way to the surface, and escape into space."

In the case of an instrument such as a horn, Prof Kurtz says, the cause of the vibrations is the musician blowing on the horn and buzzing his or her lips at a frequency that matches the natural vibrations of the horn. For the star, the vibrations start with changes in the passage of energy from the nuclear inferno in the heart of the star on its way to the surface, and escape into space.

Prof Kurtz adds: "Understanding the sounds of the stars is important for our understanding of the formation of the solar system and the Earth. We can even monitor dangerous 'active' regions on the far side of the Sun which might later send out coronal mass ejections [flares] and create geomagnetic storms, leading to power failure and radio disruption." Sun flares can occur several times a day and release more power than all of our power stations combined in a million years.

Prof Kurtz converted the usually inaudible frequency of "star music" into one that humans can hear during a public lecture at Sheffield Hallam University on Tuesday, called Songs of the Stars. The stars produce eerie whistling, African drumming, humming or rumbling sounds. He also played classical compositions by Bach using only stars as instruments of the orchestra, projected by computer, producing music that he describes as "very modern sounding but interesting." The lecture was the highlight of an international astronomy conference in Sheffield that bought together experts from around the world.

The ancient Greeks were the ones who originally predicted that planets and stars hummed as they rotated around the Universe, but the final proof that stars "sing" appeared only as recently as the 1970s, with the use of "asteroseismology".

This technique enables astronomers to look deep within the cores of stars as clearly as you can see a foetus inside a womb using ultrasound. By listening to stars, astronomers are able to keep an eye on Sun flares that may be hidden when parts of the Sun pass out of the Earth's view. These flares can actually kill astronauts.

But the power unleashed by these massive ejections is so incomprehensibly huge that nothing can be done to prevent or counteract them in the foreseeable future.

"We can't do anything about them... this is power beyond anything you can control," says Prof Kurtz.

• Natasha Tian is a PhD student from Edinburgh University who is working at The Scotsman as a BA Media Fellow.