Age of a Star Measured, Thanks to Its Earthquakes

The age of a star , a red giant nearing the end of its life, has been measured thanks to its ' earthquakes ', that is, tiny internal oscillations , and for the first time the age thus estimated has been compared with traditional techniques, which have the disadvantage of being usable only when there are other stars rotating around the first. The result demonstrates that this method, called asteroseismology , is reliable and accurate , but the implications go well beyond the simple age of a star: this technique will, in fact, allow us to analyse thousands of ancient stars in the Milky Way , and thus reconstruct the evolution of our galaxy over thousands of years. The study, published in the journal Astronomy & Astrophysics, was led by Italy thanks to the University of Bologna, with the participation of the National Institute of Astrophysics. Measuring the mass of a solitary star is very complicated: if there are no other companion stars , in fact, it is not possible to use the classic method based on the laws of gravity . But there is another way , which exploits the tiny variations in light caused by internal oscillations . " Stars vibrate in a similar way to musical instruments : acoustic waves propagate inside them and make the entire structure oscillate ," says Andrea Miglio of the University of Bologna, one of the authors of the study led by Jeppe Sinkbæk Thomsen. "These oscillations resonate at different frequencies depending on the internal properties of the star, just as the sound of an instrument depends on its shape, size and material. By studying these frequencies," Miglio continues, "we can determine its mass and therefore estimate its age."