Tiniest ‘Starquakes’ Ever Detected

In the vast expanse of the cosmos, a team of international researchers has made a groundbreaking discovery. Using the ESPRESSO spectrograph mounted at the European Southern Observatory’s (ESO) Very Large Telescope (VLT), they have detected the tiniest “starquakes” ever recorded in an orange dwarf star, Epsilon Indi (ε Indi), located 11.9 light years away.

Artist 's impression of sound waves (p modes), with different frequencies, traveling across the inner layers of a star. Credit: Tania Cunha (Planetário do Porto—Centro Ciência Viva)/Instituto de Astrofísica e Ciências do Espaço)

The team employed a technique known as asteroseismology, which measures oscillations in stars. These oscillations offer indirect insights into stellar interiors, much like how earthquakes reveal information about Earth’s interior. In ε Indi, the peak amplitude of the detected oscillations is a mere 2.6 centimeters per second, about 14% of the sun’s oscillation amplitude. This makes ε Indi the smallest and coolest dwarf star observed to date with confirmed solar-like oscillations.

The precision of these measurements is so high that the detected speed is slower than the average speed of a sloth. This level of precision could help scientists resolve a long-standing disagreement between theory and observations regarding the relationship between the mass and the diameter of cool-dwarf stars.

These “starquakes” can now be used to help plan the future European Space Agency’s (ESA) PLATO space telescope, a mission in which IA is strongly involved. The oscillation amplitudes measured in this study can be converted to amplitudes in photometry, as they will be measured by PLATO. This is a crucial piece of information to help accurately predict the seismic yield of PLATO, scheduled to be launched in 2026.

This discovery demonstrates that the power of asteroseismology can now potentially be put to use in the detailed characterization of such stars and their habitable planets. Moreover, the precise determination of the ages of nearby cool dwarfs made possible by asteroseismology may be critical in interpreting biosignatures in directly imaged exoplanets.

“Every time we open a new window into nature, new surprises drive us into new unexpected discoveries. ε Indi holds the promise of being such a window with a bright view,” comments Mário João Monteiro.

This research is published in the journal Astronomy & Astrophysics.