Helioseismology and the Exploration of the Solar Interior

June 1, 2023
3 mins read
© Photo: AURA/NSO/National Science Foundation
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As you recline on a sun-soaked beach, gazing up at the brilliant midday sky, have you ever wondered what secrets the heart of our very own star, the Sun, holds? Humans have pondered this query since the dawn of civilization, seeking to understand the processes that churn inside the Sun’s fiery core. Today, we do not have to rely on mere speculation. A revolutionary field of study known as Helioseismology allows us to explore the Sun’s interior as never before, revealing unprecedented insights into its structure, composition, and dynamic activity.

Helioseismology: A Brief Overview

Helioseismology, a term derived from Helios (the Greek god of the Sun), seismos (meaning quake), and logos (study), is a branch of astrophysics that investigates the solar interior. Similar to how geologists use seismic waves from earthquakes to study Earth’s interior structure, helioseismologists probe the Sun by studying waves that travel through its plasma body, a phenomenon known as solar oscillations.

These solar oscillations are the Sun’s natural resonances, essentially sound waves caused by the pressure changes in the Sun’s hot, gaseous envelope. They’re our Sun’s song, a celestial symphony that allows scientists to analyze and comprehend the internal machinations of our star.

Probing the Solar Interior

Helioseismology involves sophisticated data collection from both space-based observatories and ground-based telescopes. For instance, instruments like NASA’s Solar Dynamics Observatory (SDO) and the Global Oscillation Network Group (GONG) perform extensive monitoring of solar oscillations, providing invaluable data for helioseismologists.


The process of interpreting this data involves examining the speed, frequency, and other properties of the waves to determine the Sun’s internal structure. Information gathered includes density, temperature, composition, and even the mechanisms of energy transport within the Sun.


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Discoveries and Achievements

Thanks to helioseismology, we’ve unveiled various secrets hidden beneath the Sun’s glowing exterior. For instance, this discipline has confirmed that the Sun’s core rotates faster than its surface – a revelation that has profound implications for our understanding of stellar physics. It has also granted us an understanding of the Sun’s differential rotation, the process by which different latitudes of the Sun rotate at varying speeds.

Most notably, helioseismology has played a critical role in resolving the solar neutrino problem. Initially, there was a discrepancy between the theoretical predictions of neutrinos produced by nuclear fusion in the Sun’s core and the actual observations. However, through helioseismology, scientists discovered that the core conditions matched the predictions accurately, leading to the realization that neutrinos have mass and change type as they travel, resolving the puzzling discrepancy.

The Impact and Future of Helioseismology

Helioseismology has, quite literally, opened up a new dimension in our quest to understand the Sun. This has practical implications too. By studying the Sun, we can predict solar weather phenomena such as solar flares and coronal mass ejections. These events can disrupt satellite communication, power grids, and other technologies we heavily rely on. Therefore, understanding the Sun’s interior can help us mitigate the effects of such disruptive solar activities.

In the future, helioseismology will continue to refine our understanding of the Sun. New missions, such as the European Space Agency’s Solar Orbiter and NASA’s Parker Solar Probe, are expected to provide more data, enabling deeper insights into the Sun’s interior.

Moreover, the techniques developed in helioseismology have already been extended to other stars, in a field known as asteroseismology. This allows scientists to examine other stars’ interiors and compare their structures and processes with our own Sun, giving us a broader perspective of stellar behavior across the universe.

Helioseismology is a testament to human ingenuity and our unquenchable thirst to explore and understand the universe. Through this fascinating discipline, we are learning more about the Sun than our ancestors could have ever dreamt. In the grand cosmic orchestra, the Sun’s song is now more clear and informative, resonating not just in the vastness of space, but also in the data-laden charts of scientists who continue to unravel its secrets.

With every discovery, every understanding, we move closer to the Sun—not in a physical sense, but in an intellectual one. Through helioseismology, we delve into the heart of our parent star, sensing its pulse, deciphering its rhythms, and slowly uncovering the story of its life. And in the process, we better understand our place in the cosmos, under the benevolent light of our fascinating, resonating Sun.

As we cast our eyes towards the future, one can only imagine the insights yet to be uncovered about our star and others that populate the night sky. Through helioseismology and its stellar cousin, asteroseismology, we listen intently to the music of the cosmos, eager to learn more about the symphony that plays all around us. The rhythm of the stars awaits, full of hidden messages and cosmic revelations, a celestial song to which we are now finally attuned.

Click on this link to read this article in French version

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