Nearby Star's Song Shakes Up Astronomy With 'Long-Lost Tuning Fork'

Our understanding of how stars evolve has been shaken up by astronomers who have been listening to the "song" sung by a nearby star.

While the movement of celestial bodies might not quite play the "music of the spheres"—as poetically imagined by the ancient Greek philosopher Pythagoras—each star does still resonate with natural frequencies.

And just as the vibrations of earthquakes allow seismologists to probe the interior of the Earth, so the oscillations of stars allow "asteroseismologists" to learn about the inside of stars.

"The vibrations of a star are like its unique song," explained paper author and astronomer Yaguang Li of the University of Hawaiʻi at Mānoa in a statement.

"By listening to those oscillations, we can precisely determine how massive a star is, how large it is and how old it is."

Located just 21 light-years from Earth, HD 219134 is an orange main sequence star much older than our sun. By listening to its tune, astronomers have been able to learn key new information about how stars evolve as they get older.

Previous asteroseismological studies—using such NASA telescopes as Kepler and Transiting Exoplanet Survey Satellite (TESS)—have typically involved stars that are hotter than the Sun.

In contrast, HD 219134 is much cooler, meaning that its "song" was much too subtle for space-based telescopes to pick up via observation of the star's brightness.

In the new study, however, astronomers used the cutting-edge "Keck Planet Finder" (KPF) instrument as the W. M. Keck Observatory at the peak of Mauna Kea, Hawaii, to measure the faint movement of the surface of HD 219134 towards and away from us.

"KPF's fast readout mode makes it perfectly suited for detecting oscillations in cool stars," explained Li. "It is the only spectrograph on Mauna Kea currently capable of making this type of discovery."

Taking more than 2,000 ultra-precise measurements of the star's vibrations of the course of four consecutive nights, the team have been able to estimate HD 219134's age and size.

Based on how it has been observed oscillating, Li and colleagues believe that HD 219134 is more than twice as old as our sun, at a stately 10.2 billion years.

Not only does this make it one of the oldest stars to have ever been dated via asteroseismology, but it also shakes up how we understand how stars age.

For most stars, astronomers are able to calculate their ages based on how quickly they spin, in a method known as "gyrochronology;" for while young stars spin quickly, they lose angular momentum over time, slowing down.

However, the slow-down of stars like HD 219134 tends to tall at older ages. By better understanding how this process works, astronomers will be able to refine our estimates of the ages of numerous other stars across the sky.

"This is like finding a long-lost tuning fork for stellar clocks," said Li. "It gives us a reference point to calibrate how stars spin down over billions of years."

This wasn't the only surprising development from the new analysis of HD 219134—as the team also found that the star is more compact than previously assumed.

Specifically, past studies based on interferometry (wherein the size of stars are measured using observations by multiple telescopes) gave it a radius some 4 percent larger.

The reason for this discrepancy is unclear—but could point to issues with some of the assumptions presently made in stellar modeling.

The researchers were also able to confirm that, of the five planets orbiting HD 219134, two indeed have Earth-like compositions, with solid, rocky surfaces.

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Reference

Li, Y., Huber, D., Ong, J. M. J., van Saders, J., Costa, R. R., Larsen, J. R., Basu, S., Bedding, T. R., Dai, F., Chontos, A., Carmichael, T. W., Hey, D., Kjeldsen, H., Hon, M., Campante, T. L., Monteiro, M. J. P. F. G., Lundkvist, M. S., Saunders, N., Isaacson, H., ... Walawender, J. (2025). K Dwarf Radius Inflation and a 10 Gyr Spin-down Clock Unveiled through Asteroseismology of HD 219134 from the Keck Planet Finder. The Astrophysical Journal, 984(2), 125. https://doi.org/10.3847/1538-4357/adc737