Stars as Laboratories for Fundamental Physics - MPP Theory Group

Chapter 11
Supernova Neutrinos
The general physical picture of stellar collapse and supernova (SN)
explosions is described with an emphasis on the properties of the observable
neutrino burst from such events. The measurements of the
neutrino burst from SN 1987A are reviewed. Its lessons for particle
physics are deferred to Chapter 13 except for the issue of neutrino
masses and mixings. Future possibilities to observe SN neutrinos are
discussed.
11.1 Stellar Collapse and Supernova Explosions
11.1.1 Stellar Collapse
A massive star (M > ∼ 8 M ⊙ ) inevitably becomes unstable at the end
of its life. It collapses and ejects its outer mantle in a SN explosion
as briefly described in Sect. 2.1.8. Within fractions of a second the
collapsing core forms a compact object at supranuclear density which
radiates its gravitational binding energy E b ≈ 3×10 53 erg within a few
seconds in the form of neutrinos. Gamow and Schoenberg (1940, 1941)
were the first to speculate that neutrino emission would be a major
effect in the collapse of a star. The only direct observation of neutrinos
from such an event occurred on 23 February 1987 when the blue supergiant
Sanduleak −69 202 in the Large Magellanic Cloud exploded in
what became known as SN 1987A. The neutrinos, and possibly other
low-mass particles, emitted from a collapsing star are the main topic of
this chapter, with SN 1987A playing a primary role.
Before an evolved massive star collapses, its core is a degenerate
configuration made up of iron-group elements. They cannot release
nuclear energy by fusion as they are already the most tightly bound
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