Four Decades of Listening to the Sun
For forty years, a network of telescopes has been listening to the Sun hum. Scientists from the University of Birmingham and Yale University have finally decoded what those subtle vibrations reveal about our star's hidden interior. A new study has found that the Sun's internal structure quietly shifts between solar cycles, producing measurable changes deep beneath its surface that function like a rhythmic heartbeat pulsing through the stellar interior.
The discovery, based on helioseismology data collected over four complete solar cycles, reveals patterns in the Sun's internal oscillations that had not been previously identified. These patterns show that the Sun's core and radiative zone undergo structural changes that are synchronized with the 11-year solar activity cycle but manifest in ways that are distinct from the surface phenomena like sunspots and solar flares that astronomers have long studied.
How Helioseismology Works
Just as geologists use seismic waves to probe Earth's interior, solar physicists use the Sun's natural oscillations to study its internal structure. The Sun is constantly vibrating, with millions of acoustic waves bouncing through its interior. These waves cause the solar surface to rise and fall by tiny amounts that can be detected by sensitive instruments on Earth and in space.
By analyzing the frequencies, amplitudes, and travel times of these waves, researchers can construct detailed maps of the Sun's internal conditions, including temperature, density, and rotation speed at different depths. The technique, known as helioseismology, has been one of the most powerful tools in solar physics since its development in the 1970s and 1980s.
The new study leveraged the exceptionally long baseline of data now available. Forty years of continuous observations provide the statistical power needed to detect subtle changes that shorter studies would miss.
