They had been alerted to the system by amateur Japanese astronomers who had spotted that V407 Cygni had increased in brightness by 10 times over just a few days.

BBC: Gamma rays from nova explosion surprise astronomers

Now, an international team of astronomers has trained the Fermi space-based gamma ray telescope on V407 Cygni, a "binary" system comprising a white dwarf star and a red giant companion, 9, 000 light-years away.

BBC: Gamma rays from nova explosion surprise astronomers