How ‘music’ from stars can help measure distances to things in space

For long, measuring the exact distance to celestial objects has been an important goal and one of the biggest challenges for astronomers. Now, in a breakthrough study, a team of astronomers has used asteroseismology, or the study of stellar oscillations, to accurately measure the distance of stars from the Earth.

For this study, published recently in the journal Astronomy & Astrophysics, the researchers used data from the Gaia mission by the European Space Agency, which was launched 10 years ago. The data collected by the Gaia satellite provided astronomic measurements including position, distance from the Earth and movement of nearly two billion stars, a press statement from École polytechnique fédérale de Lausanne’s (EPFL) explains.

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Currently, scientists use parallaxes—the difference in the apparent position of an object viewed along two different lines of sight—to measure the distance to stars. Using Gaia’s satellite, parallax angles were measured through a form of triangulation between Gaia's location in space, the Sun and the star in question. The farther away a star is, the more difficult the measurement because parallax gets smaller the larger the distance, the statement explains.

The team of scientists from EPFL and the University of Bologna, in Italy, performed calculations on over 12,000 oscillating red giant stars, which is the biggest sample size and most accurate measurements to date. They used asteroseismology, and specifically stars' vibrations and oscillations, to better understand their physical properties.

Stellar oscillations are measured as tiny variations in light intensity and translated into sound waves. This leads to a frequency spectrum of these oscillations which helps astronomers determine how far away a star is, the statement adds.

For this study, the astronomers listened to the 'music' of millions of stars— some of them 15,000 light-years away. "By analyzing the frequency spectrum of stellar oscillations, we can estimate the size of a star, much like you can identify the size of a musical instrument by the kind of sound it makes—think of the difference in pitch between a violin and a cello," study author Andrea Miglio explains in the statement.

Then the astronomers determined its luminosity and compared it to the luminosity perceived here on Earth. They analysed these data along with temperature and chemical composition readings obtained from spectroscopy to calculate the distance to the star. In the final step, astronomers compared the parallaxes obtained in this process with those reported by Gaia to check the accuracy of the satellite's measurements.

"Asteroseismology is the only way we can check Gaia's parallax accuracy across the full sky—that is, for both low- and high-intensity stars," lead author Richard Anderson explains in the statement.

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