Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-11-20
Astronomy and Astrophysics
Astrophysics
Paper presented at IAU-GA, Prague, August 2006
Scientific paper
10.1017/S1743921307000567
Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing 3He, which they mix into the convective envelope on the giant branch and distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the observed cosmic abundance of 3He with the predictions of Big Bang nucleosynthesis. In this paper we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell. In this zone the burning of the 3He left behind by the retreating convective envelope is predominantly by the reaction 3He + 3He -> 4He + 2p, a reaction which, untypically for stellar nuclear reactions, {\it lowers} the mean molecular weight, leading to a local minimum. This local minimum leads to Rayleigh-Taylor instability, and turbulent motion is generated which will continue ultimately up into the normal convective envelope. Consequently material from the envelope is dragged down sufficiently close to the burning shell that the 3He in it is progressively destroyed. Thus we are able to remove the threat that 3He production in low-mass stars poses to the Big Bang nucleosynthesis of 3He. Some slow mixing mechanism has long been suspected, that connects the convective envelope of a red giant to the burning shell. It appears to be necessary to account for progressive changes in the 12C/13C and 14N/12C ratios on the First Giant Branch. We suggest that these phenomena are also due to the Rayleigh-Taylor-unstable character of the 3He-burning region.
Dearborn David S.
Eggleton Peter P.
Lattanzio John C.
No associations
LandOfFree
The Destruction of 3He by Rayleigh-Taylor Instability on the First Giant Branch does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Destruction of 3He by Rayleigh-Taylor Instability on the First Giant Branch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Destruction of 3He by Rayleigh-Taylor Instability on the First Giant Branch will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-120008