(Submitted April 24, 1998)
How long does a supernova last?
There is no single answer to your question.
In a sense, the explosion itself is over within a matter of seconds.
But the envelope of the dying star is expelled with such speed that,
when it ploughs into the interstellar gas, it is heated to millions
of degrees and remain bright in X-rays for tens of thousands of years.
In the visual light, how long you can track supernovae depends on their
distance. Supernova 1987A in the Large Magellanic Cloud (which is relatively
nearby as these things go) is still being followed from the ground and from
the Hubble Space Telescope:
for Ask an Astrophysicist