New evidence shows many stars are experiencing irregularities at their core – Zoo House News
Astronomers have found a way to peek into the physics of some of the brightest stars in the sky.
Using data from NASA’s Kepler space telescope, an international team of researchers has found new evidence that red giants, dying stars that have exhausted their hydrogen supplies and are in the final stages of stellar evolution, often experience large-scale structural variations, or whatever are known as “glitches” deep down at their core.
The media-told stellar perturbations have to do with a star’s rotation, but lead author Mathieu Vrard is investigating a different type of defect. The perturbations in this study can affect a star’s vibrations or the frequencies and paths traveled by sound waves as they pass through a star.
Red cluster stars, objects with burning helium cores, are often used as rangefinders in astrophysical studies to measure aspects such as galaxy densities and to learn more about the physical processes behind stellar chemical evolution. So it’s important for scientists to understand why these discontinuities occur, said Vrard, a postdoctoral researcher in astronomy at Ohio State University.
“By analyzing these variations, we can use them to get not only the global parameters of the star, but also information about the precise structure of these objects,” he said.
The study, recently published in the journal Nature Communications, is the first to perform detailed observational characterizations of the deepest layers of these red giants.
To determine whether these perturbations are more common among certain groups of stars, the team selected a sample of 359 red giants that were below a certain stellar mass and measured various properties and individual frequencies of each star.
The team found evidence that 24 of the red giants surveyed (about 7% of those in the sample) had experienced intermittent structural discontinuities at one point or another during their lives. While 7% may not seem like a lot, when applied to all known stars in our Universe, the number of stars exhibiting these irregularities would be enormous.
There are two main theories that explain how these disorders might work. The first scenario assumes that glitches are present throughout the star’s evolution, but are generally very faint and below the threshold that astronomers would classify as true discontinuities.
The second suggests that irregularities are “smoothed out” by an unknown physical process that later leads to changes in the structure of the star’s core.
As it turns out, the first scenario isn’t supported by this study’s model, which predicts observed disturbances to actually be a common occurrence, but more accurate data is needed before scientists can confidently subscribe to the second.
“We think the second theory might hold up better because the first didn’t make sense based on our observations,” Vrard said.
Because the study provides a better characterization of the physical processes taking place inside red giant stars, Vrard’s work could potentially have major implications for the field of asteroseismology — a branch of astronomy that studies the internal composition of stars using the oscillations of sound waves — and for galactic archaeology, a field that uses detailed records of stellar fossils to unravel the history of the universe.
And although Vrard’s current analysis is over, he wants to build on what the scientific community knows about red giant stars by examining more detailed data that could help cultivate even more refined stellar models.
This work was supported by both NASA and the European Regional Development Fund.
Materials provided by Ohio State University. Originally written by Tatiana Woodall. Note: Content can be edited for style and length.