Man staring into the stars

Man staring into the stars

EVANSTON, Ill. — Scientists may be able to sound effects to the classic nursery rhyme “Twinkle, Twinkle, Little Star.” Researchers from Northwestern University have simulated the sound of a star’s twinkle, revealing that the brightest celestial bodies in space resemble a “warped ray gun.”

It’s long been established that the twinkling of stars we see from Earth results from our atmosphere distorting the starlight. However, new research has revealed an inherent “twinkle” in stars, caused by gas waves rippling across their surfaces, a phenomenon that remains undetected by current telescopes on Earth.

Now, the team has crafted the first 3D simulations of energy waves flowing from the core to the outer surface of a massive star. Using these cutting-edge models, researchers calculated the innate twinkling extent of stars for the first time.

“Motions in the cores of stars launch waves like those on the ocean. When these waves reach the star’s surface, they cause a distinctive twinkling that astronomers might be able to observe,” says the study’s lead author, Dr. Evan Anders, in a university release. “For the first time, we have developed computer models which 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 researchers explain that all stars possess a convection zone, a chaotic region where gases stir and drive heat outward. For massive stars — those at least 1.2 times the mass of our Sun — this convection zone is located at their cores.

“Convection within stars is similar to the process that fuels thunderstorms. Cooled air drops, warms, and rises again. It’s a turbulent process that transports heat,” Dr. Anders explains.

He adds that this process also creates waves, little currents that alter starlight’s brightness, resulting in a faint twinkle. Since the cores of massive stars are concealed from view, Dr. Anders and his team set out to model this hidden convection. Their latest simulations integrate all pertinent physics to accurately predict a star’s brightness fluctuation due to convection-induced waves.

While some waves reach the star’s surface, creating the twinkling effect, others remain trapped, bouncing around within the star. To identify the waves responsible for twinkling, the researchers devised a filter that describes the wave activity inside the simulations.

“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 says.

He drew parallels to a music studio, where soundproofing minimizes extraneous acoustics, enabling musicians to capture the “pure sound” of their music.

The research team applied their unique filter to the pristine waves emanating from the convective core. They monitored the waves ricocheting within a model star, ultimately discovering that their filter accurately portrayed the transformation of waves originating from the core.

Subsequently, they developed a distinct filter to predict wave behavior within an actual star. Once the filter was applied, the resultant simulation demonstrated how astronomers expect waves to appear if observed through a powerful telescope.

“Stars get a little brighter or a little dimmer depending on various things happening dynamically inside the star. But powerful future telescopes may be able to detect it,” adds Dr. Anders.

Expanding on the analogy of a recording studio, Dr. Anders and his team utilized their simulations to generate sound. As the waves exist beyond the human hearing range, the scientists uniformly increased the frequencies to make them audible.

Depending on a massive star’s size or brightness, Dr. Anders noted that the convection gives rise to waves corresponding to different sounds. Waves originating from a giant star’s core resemble the sounds of a “warped ray gun reverberating through an alien landscape.” However, these sounds transform as they reach the star’s surface. In the case of a large star, the ray-gun-like pulses transition into a “low echo in an empty room.”

The surface waves of a medium-sized star invoke visions of a “persistent hum across a windswept terrain.” Conversely, surface waves from a small star sound like a “mournful weather siren.”

The team routed songs through stars of different sizes to understand how they altered the music. They transmitted a brief audio clip from “Jupiter,” a movement from Gustav Holst’s orchestral suite “The Planets,” and “Twinkle, Twinkle, Little Star” through three types of massive stars.

“We were curious how a song would sound if heard as propagated through a star,” Anders concludes. “The stars change the music and, correspondingly, change how the waves would look if we saw them as twinkling on the star’s surface.”

This study is published in the journal Nature Astronomy.

South West News Service writer Stephen Beech contributed to this report.

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