University of California, Santa Barbara | 2019 Oct 28
New findings detail a method for investigating the inner workings of stars in a rare phase
in five billion years or so, when the sun has used up the hydrogen in its core, it will inflate and turn into a red giant star. This phase of its life — and that of other stars up to twice its mass — is relatively short compared with the more than 10 billion-year life of the sun. The red giant will shine 1000 times brighter than the sun, and suddenly the helium deep in its core will begin fusing to carbon in a process called the “helium core flash.” After this, the star settles into 100 million years of quiet helium fusion.
Astrophysicists have predicted these flashes in theory and in models for 50 years, but none has ever been observed. However, a new study ... suggests this may soon change. ...
Helium core flash plays an integral role in our understanding of the life cycles of low-mass stars. Unfortunately, gathering data from the cores of distant stars is incredibly difficult, so scientists have been unable to observe this phenomenon. ...
The new and promising angle detailed in the paper is that the astronomers have been studying the processes in a very special — and up to now not very well understood — type of star designated a subdwarf B star. These are former red giants that, for unknown reasons, have lost most of their outer layer of hydrogen. Subdwarf B stars provide scientists a unique opportunity to more directly probe the hot core of a star. What’s more, the remaining thin layer of hydrogen is not thick enough to dampen the oscillations from the repeated helium core flashes, giving the researchers a chance to potentially observe them directly. ...
Asteroseismic Signatures of the Helium Core Flash ~ M. M. Miller Bertolami et al
- Nature Astronomy (online 30 Sep 2019) DOI: 10.1038/s41550-019-0890-0
