Vibrations echoing through giant stars are offering unexpected insights into their internal structures and evolutionary paths. New findings published in Nature and based on data from NASA’s Kepler K2 mission suggest that certain stars become trapped in a kind of musical loop during their later stages—an effect that could help astronomers better understand the history of the Milky Way.
The Symphony Of Starquakes
Stars don’t just shine—they also sing. Vibrations known as starquakes, caused by bubbles of hot gas bursting on a star’s surface, ripple through the entire body, creating a unique set of resonant frequencies. These stellar tremors, detectable as subtle variations in brightness, help scientists decode a star’s inner workings.
“We can detect these vibrations, which occur at specific ‘resonant frequencies’, by looking for subtle variations in the brightness of the star,” explained Science Alert, “by studying the frequencies of each star in a group called a cluster, we can tune into the cluster’s unique ‘song’.”
Why M67 Matters?
Clusters like M67 are astrophysical goldmines. Since all the stars in a cluster formed around the same time from the same cosmic cloud, astronomers can compare them directly to study how stars evolve. In the case of M67, the cluster also has a bonus: many of its stars have a similar chemical composition to our Sun, making it an ideal testbed for solar-like evolution.
Using this setup, researchers noticed something strange. In these red giants, a group of resonant frequencies known as “small spacings” behaved in a way no one had predicted. Initially, these spacings changed as expected—getting wider or narrower depending on the depth of the hydrogen-burning shell inside the star.
The Sound That Stalls
One of the study’s most surprising discoveries is what the authors call a “stalled note”—a moment when the spacing between certain frequencies freezes rather than evolving.
This occurs when a star’s convective envelope, its outer boiling layer, penetrates about 80% of the star’s mass and meets a turbulent internal boundary. The abrupt change in sound speed at this transition appears to lock the star’s frequencies into place temporarily.
When Stars Sing The Same Note On Loop
Stars aren’t silent. Inside many of them, including our Sun, bubbles of hot gas rise and burst in the outer layers, sending waves rippling through their interiors. These starquakes cause stars to vibrate at precise frequencies—cosmic echoes that astronomers can measure by tracking changes in brightness.
In a recent study published in Nature, scientists used data from the Kepler space telescope’s K2 mission to explore these vibrations in the M67 star cluster, located about 3,000 light-years away.
What they found was unexpected: stars in the giant phase of their life cycle appear to get “stuck,” resonating with the same acoustic signature over and over.
It’s as if the stars are replaying a single fragment of a larger melody—a repetitive rhythm that reveals more about their internal structure than previously thought.
