"Music" from stars can be used to measure distances in space

In a breakthrough study, astronomers have harnessed asteroseismology – the study of stellar oscillations – to measure the distance between stars and Earth with remarkable accuracy. The experts compare this technique to using the “music” of stars.

The team applied this method to thousands of stars, cross-verifying measurements from the Gaia mission’s exploration of the near Universe.

Gaia mission

The night sky is a mosaic of celestial bodies – stars, planets, distant suns, and galaxies billions of light years away. Discerning their exact distances from Earth is a significant challenge and a key objective for astronomers. 

This pursuit led to the launch of the European Space Agency’s Gaia mission a decade ago. Gaia’s satellite has since provided astronomical data on nearly two billion stars, improving our understanding of their positions, distances, and movements.

At the Swiss Federal Institute of Technology Lausanne (EPFL), Professor Richard Anderson’s research group is focused on measuring the expansion of the Universe using Gaia as an instrumental tool.

“Gaia increased by a factor of 10,000 the number of stars whose parallaxes are measured thanks to a massive gain in accuracy over its predecessor, the ESA Hipparcos mission,” said Professor Anderson.

Parallax measurements

Parallaxes are fundamental in calculating star distances. This technique involves triangulating Gaia’s location in space, the Sun, and the star in question. However, measuring parallax becomes increasingly challenging with distant stars.

Despite Gaia’s success, its parallax measurements are complex and subject to small systematic errors. To address this, the research team conducted calculations on over 12,000 oscillating red giant stars, creating the most extensive and accurate sample to date.

“We measured the Gaia biases by comparing the satellite’s parallax reports with those we determined using asteroseismology,” explained study lead author Saniya Khan, a scientist in Anderson’s group. This research, published in the journal Astronomy & Astrophysics, marks a significant leap in celestial measurements.

Frequency spectrum 

Asteroseismology functions similarly to how geologists use earthquakes to understand Earth’s structure. Astronomers analyze stars’ vibrations and oscillations, which manifest as variations in light intensity. These are translated into sound waves, forming a frequency spectrum of the oscillations.

“The frequency spectrum lets us determine how far away a star is, enabling us to obtain asteroseismic parallaxes,” said Khan. “In our study, we listened to the ‘music’ of a vast number of stars – some of them 15,000 light-years away!”

This process involves understanding the propagation speed of sound waves in space, which varies based on the star’s interior temperature and density.

Study significance

“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 violon and a cello,” said study co-author Professor Andrea Miglio from the University of Bologna.

The team then compared the luminosity of stars with perceived luminosity on Earth, coupling this with temperature and chemical composition data obtained through spectroscopy. Sophisticated analyses of these data allowed them to calculate star distances accurately.

“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,” explained Anderson.

Future research

Going forward, missions like TESS and PLATO will use asteroseismology for exoplanet detection and survey, expanding dataset coverage across vast sky regions. 

“Methods similar to ours will therefore play a crucial role in improving Gaia’s parallax measurements, which will help us pinpoint our place in the Universe and benefit a plethora of subfields of astronomy and astrophysics,” said Khan.

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