# Suppose that a 15 M(solar masses) star finally runs

Subject: Physics    / General Physics

You should use your knowledge of physics to estimate answers perhaps only to an order of magnitude, using very basic data. You are not expected to undertake research to find the answers.

Suppose that a 15 M(solar masses) star finally runs out of nuclear fuel in its core and undergoes a Type II supernova explosion. You are going to analyse the energy budget, calculating all the quantities in Joules.

a) Estimate the amount of gravitational energy that would be liberated by the collapse of the core (say) 1.4 M(solar masses) to the size of neutron star.

b) How much of this energy would be required to disintegrate the iron nuclei in the core?

c) How much of this energy would be required to provide the kinetic energy of the ejecta if a typical velocity for the ejecta in the initial stage of a supernova explosion is up to 0.1c?

d) The absolute visual magnitude at maximum of a typical supernova is comparable to that of a modest galaxy for a few weeks. Estimate the total light output of the supernova.

e) Compare this with the other aspects of the energy budget available and comment on any deficit.