Exploring globular clusters with the lens of asteroseismology

Thu, 23 Jun 2022 04:29:16 GMT
Space Daily

Bologna, Italy (SPX) Jun 23, 2022 Asteroseismology - one of the most fascinating and sophisticated...

Asteroseismology - one of the most fascinating and sophisticated methods for measuring the mass of stars, and by extension, their age - can also be successfully used to reveal the characteristics of the stars within globular clusters: very large groups of stars condensed in a relatively small space and all at approximately the same distance from us.

"But Asteroseismology can also play a crucial role in this respect, thanks to its ability to provide a direct and accurate estimate of the mass, radius, age, and some other features of the stars belonging to the individual populations in a globular cluster."

"Indeed, Asteroseismology makes it possible to determine the mass and age of stars through the study of stellar oscillations, which are measured by means of the luminosity variations observed on the surface of the stars, which are then analyzed using refined mathematical methods," explains Enrico Corsaro, a researcher at the INAF - Astrophysical Observatory of Catania and second author of the study.

The study analyzed a sample of 37 stars within M4: currently the highest number for this kind of study for the distant globular clusters.

Of these, most are red giants, very bright stars in the advanced stages of their evolution, having small or intermediate mass, while the other 6 are horizontal branch stars, a later evolutionary stage composed of stars that are burning helium in their cores.

"Moreover, the results obtained are in agreement with other estimates made with more traditional methods: a confirmation of the efficiency and robustness of the asteroseismic method also for the study of stars within globular clusters".

In the first population, the stars have similar chemical characteristics to those outside the cluster, while stars in the second have completely different chemical characteristics: it is in fact a stellar population born from the material ejected from the stars of the first population.

The relationship between their mass and temperature was identified in the sample, thus obtaining the first direct confirmation of the behavior already predicted for these stars by theoretical stellar evolution.

"Since horizontal branch stars are the direct descendants of red giants, studying their mass has allowed us to have important information on what happens during the earlier phase, in particular we also got information on the phenomenon of mass loss, occurring during the ascent of the red giant branch," explains Tailo.

"In this context, the amount of mass loss that stars in globular clusters undergo is much higher than that of their counterparts in less dense systems or for stars not belonging to stellar associations, a result that has involved many astronomers and astrophysicists in various interdisciplinary studies."

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