The Milky Way, for instance, gobbled up smaller galaxies during its evolution astrophysicists know this because chemical abundances in stars trace their ancestry.

“And the only way you can know its age is by knowing the age of the host star,” Deheuvels said.Īnother field that requires precise stellar ages is galactic archaeology, the study of how galaxies are assembled. The next step is to characterize those worlds and determine if they’re suitable for life. Since 1992, scientists have spotted more than 5,400 exoplanets. Take the search for extraterrestrial life. But first “we want to find the number of red giants that show this behavior and compare them to different scenarios for the formation of these magnetic fields,” Deheuvels said.Īnd age is not just a number, but a tool that could help answer some of the most profound questions about the cosmos. Here, the team explored how those fields affected the properties of g-modes-which, Deheuvels noted, may provide a way to move beyond red giants and detect magnetic fields in stars that don’t show those rare asymmetries. A second study, led by Deheuvels, used mixed-mode asteroseismology to detect magnetic fields in the cores of 11 red giants. Deheuvels thinks this result suggests that the star’s magnetic field is tipped on its side, meaning that the technique could determine the orientation of magnetic fields, which is crucial for updating models of stellar evolution. “We were a bit puzzled,” said Sébastien Deheuvels, a study author and an astrophysicist at Toulouse. However, one of the three red giants surprised them: Its mixed-mode signal was backward. Li and his colleagues found a giant trio that exhibited the predicted asymmetries, and they calculated that each star’s magnetic field was up to “2,000 times the strength of a typical fridge magnet”-strong, but consistent with predictions. Bugnet and others had predicted that magnetic fields would break that symmetry, but no one was able to make that tricky observation-until Li’s team. Typically, mixed-mode oscillations in red giants occur almost rhythmically, producing a symmetric signal. The mixed modes are the tool that probes the heart of a star-they allow astronomers to see the g-mode oscillations-and they’re only detectable in red giant stars. Studying mixed modes revealed that red giant cores rotate much more slowly than the star’s gaseous envelope, contrary to what astrophysicists had predicted. In 2011, the KU Leuven astrophysicist Paul Beck and colleagues used Kepler data to show that in red giants, p-modes and g-modes interact and produce what’s known as a mixed mode. For stars like our sun, p-modes dominate their observable oscillations their g-modes, which are affected by internal magnetic fields, are too weak to detect and can’t reach the star’s surface. They come in two basic flavors: acoustic pressure modes (p-modes), which are sound waves that move through the outer regions of a star, and gravity modes (g-modes), which are lower in frequency and mostly confined to the core. Its sensitivity allowed astrophysicists to detect minute changes in starlight linked to stellar oscillations, which affect both the radius and the brightness of the star.īut decoding stellar oscillations is tricky. To study quaking giants, scientists use data from NASA’s planet-hunting Kepler telescope, which monitored the brightness of over 180,000 stars for years.

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