The Northwestern University-led team has developed the first 3D simulations of energy rippling from a massive star's core to its outer surface. Using these new models, the researchers determined, for the first time, how much stars should innately twinkle.
The team then converted these gas waves into sound waves, enabling listeners to hear both what the insides of stars and the "twinkling" should sound like.
"Motions in the cores of stars launch waves like those on the ocean," said Evan Anders, who led the study. "When the waves arrive at the star's surface, they make it twinkle in a way that astronomers may be able to observe.
"For the first time, we have developed computer models that allow us to determine how much a star should twinkle as a result of these waves. This work allows future space telescopes to probe the central regions where stars forge the elements we depend upon to live and breathe."
The innate twinkling of stars is not caused by the Earth's atmosphere, as some might believe, but by the waves of gas on their surface. These waves are caused by a star's convection zone, where gases churn to push heat outward. For massive stars, this zone resides at their cores.
As the cores of massive stars cannot be seen from Earth, the research team recreated the convention process to accurately predict how a star's brightness changes depending upon convection-generated waves.
"We first put a damping layer around the star – like the padded walls you would have in a recording studio – so we could measure exactly how the core convection makes waves," Anders explained.
Using this technique, the team was able to accurately describe how a star changed the waves coming from the core, and were able to simulate them. In order to generate sound, the team uniformly increased the frequencies of the waves until they were audible.
The researchers found that stars produce different sounds depending on their size and brightness. While waves emerging from large stars are described as sounding like a warped ray gun, the sound of a medium-sized star resembles a persistent hum through a windswept terrain. Surface waves on a small star reportedly sound like a plaintive alert from a weather siren.
Next, Anders and his team passed songs through different stars to listen to how the stars change the songs.
The team passed a short audio clip from 'Jupiter' (a movement from 'The Planets' orchestral suite by composer Gustav Holst) and 'Twinkle, Twinkle, Little Star' through three sizes (large, medium and small) of massive stars.
"We were curious how a song would sound if heard as propagated through a star," Anders said. "The stars change the music and, correspondingly, change how the waves would look if we saw them as twinkling on the star's surface."
The study was published in the journal Nature Astronomy.
