Eur. Phys. J. C http://doi.org/bj6w (2016)

Detecting neutrinos is hard at the best of times, but detecting neutrino bursts from supernovae — the relatively rare astronomical events that occur when a massive star has exhausted its nuclear fuel and collapses — is harder still. The celebrated 1987A core-collapse supernova (SN 1987A) is, to date, the only supernova from which neutrinos have ever been detected. Since 1987, detection capabilities for supernova neutrinos have increased dramatically — all we need to uncover a great deal more new physics and astrophysics is another core-collapse supernova to occur near planet Earth.

Of course, the huge distances travelled by supernova neutrinos from a star to the Earth means that careful thought is required to predict and interpret their detection signatures. As Jörn Kersten and Alexei Smirnov showed, that also extends to their quantum mechanical description as wave packets: on their way to Earth, neutrino wave packets spread and separate over macroscopic length scales, and can reach coherence lengths comparable to the radius of the Earth. The authors considered these features and their consequences, uncovering a 'catch-up' effect that leads to an increase in the coherence length as the neutrinos cross the core of the Earth.