Death throes of massive stars

Abstract

MASSIVE stars undergo violent deaths, forming the type II supernovae believed to result from gravitational collapse of the stellar cores. Such an event may be recognised by the optical outburst which occurs when the thermal and kinetic energy generated by the collapse propagates to the stellar photosphere. This occurs ∼5–20 d after the collapse¹. However, the optical data are incomplete in the sense that supernovae are invariably discovered at or shortly after peak optical intensity so only the decline from maximum brightness has been recorded in any detail. In addition, various theoretical models suggest that the optical radiation will be preceded by bursts of other forms of energy (neutrinos, gravitational waves, γ and X rays). Detection of these bursts, as well as of the early part of the optical light curve, would be greatly facilitated if the occurrence of a supernova could be predicted on the basis of the pre-supernova behaviour of the star. We show here that neutrino emission in the final stages of nuclear burning (as originally proposed by Morrison²) could, in principle, provide such a warning, though the current practical limitations are severe.