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Issue 6.09

The Astrophysics Spectator

October 7, 2009

Supernovae within the Milky Way occur at a rate of about 1 ever 50 years.  This does not give us much opportunity to study supernovae at close range.  The closest supernova over the past half century appeared in 1987 in the Large Magellanic cloud.  Occurring only 50 kpc from Earth in a dwarf galaxy relatively unobscured by dust, this supernova is the best studied supernova we have.  Its progenitor, a blue supergiant, was observed on many occasions before the explosion, including just hours before the explosion, and the explosion itself was observed just hours after it commenced.  Most important, neutrinos released by this supernova were detected by several neutrino detectors, confirming the basic theory for most supernovae—an explosion occurs when the core of a massive star collapses.

This issue of the web site contains a page describing the observation of neutrinos from SN 1987A.  The page describes how these neutrinos were observed and what was learned from them.

In the next update to the web site, I will discuss the other observations of SN 1987A, including the unsuccessful searches for a radio pulsar at the site of the explosion.

Jim Brainerd

Supernovae

Neutrinos and Supernova 1987A.  A core-collapse supernova releases most of its energy as neutrinos.  This theoretical conclusion is confirmed by a single event, the supernova seen in the Large Magellanic Cloud in 1987.  Large neutrino detectors buried deep underground detect cosmic neutrinos by looking for neutrino collisions with electrons.  Three neutrino detectors saw a handful of these collisions by neutrinos traveling from the direction of the Large Magellanic Cloud just before a blue supergiant star in the nearby dwarf galaxy exploded.  The energy carried by these neutrinos is consistent with the energy generated in the core-collapse of a massive star.  (continue)

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