NASA is using the Transiting Exoplanet Survey Satellite (TESS) to study mysterious pulsations of a star known as Delta Scuti. Using TESS, astronomers have been able to detect pulsation patterns in dozens of young and rapidly rotating stars. Astronomers believe the discovery will help revolutionize their ability to study details like ages, sizes, and compositions of the stars. This class of stars is named for the first of their type discovered, Delta Scuti.
Delta Scuti stars pulsate in interesting ways, but the patterns of those pulsations have defied the understanding of scientists. Tim Bedding, a professor of astronomy at the University of Sydney, said, “To use a musical analogy, many stars pulsate along simple chords, but Delta Scuti stars are complex, with notes that seem to be jumbled. TESS has shown us that’s not true for all of them.”
Scientists are applying some techniques that geologists use when studying seismic waves from earthquakes to learn about the internal structure of the Earth. Applying the same principle to the interior of stars, astronomers study star pulsations in a field called asteroseismology. Sound waves can travel through the interior of a star at speeds that change with depth. The waves combine and pulsation patterns at the surface of the star.
Astronomers can detect these patterns as tiny fluctuations in brightness and use them to determine the star’s age, temperature, composition, internal structure, and other properties. Delta Scuti stars are between 1.5 and 2.5 times the Sun’s mass, and their namesake star is visible to the human eye in the southern constellation of Scutum.
Typically, scientists have trouble interpreting star pulsations. The stars rotate once or twice a day, at least a dozen times faster than the Sun. TESS was able to monitor large swaths of the sky for 27 days at a time, taking images every 30 minutes with each of its four cameras. Exposures every 30 minutes were too slow to catch the pulsations, so TESS imaged Delta Scuti stars every two minutes to capture the changes happening. This led to scientists discovering a subset of Delta Scuti stars with regular pulsation patterns.
Knowing what to look for, the team search for other examples in Kepler data and identified 60 Delta Scuti stars with clear patterns. The breakthrough allows scientists to understand and compare the stars with models, which is something they’ve never been able to do.