In stars, an instability phenomenon, reminiscent of the
→ thermohaline convection in the oceans, that takes place
when layers of higher molecular weight occur above a region of lower
molecular weight. A situation of heavier material being above lighter
gas in a star can occur during the → helium flash
when → helium burning
does not start in the center but in the shell.
Similarly, in → close binary
systems it may happen that helium-rich material is transferred
to a → main sequence star. Then a helium-rich outer layer is
formed and the instability occurs at the interface between that layer and the
original stellar material. This process can explain several surface abundance
variations in stars. First discussed by S. Kato (1966, Publ. Astron. Soc. Japan
18, 374).
See also: → thermohaline; → mixing.
