Blazars and nuclear physics! How are studies on blazars related to the field of nuclear physics? Should these not purely belong to Astrophysics? Just inquisitive.
 A: I'm not that firm with the concept of blazars, but as with all super-massive astrophysical objects like neutron stars, black holes and all their subclasses, their heaviness forces the particles to highly-relativistic states. There you just can't use the hypothesis of "charged billiard balls" for atoms any more - a neutron star for example is only stable because of the Pauli pressure, a purely quantum mechanical/nuclear physical effect.
On a more general level: What is "purely astrophysical"? Astronomy and Astrophysics is more or less by definition the synthesis of all other parts of physics applied to observations from the whole universe instead of just our earth. For star/galaxy spectrums you need the atom physics results to identify the spectra. For accredition discs and stellar/planetal evolution you need gas/fluid dynamics, depending on the case including relativistics and/or magnetic fields. Radioastronomy uses classical or relativistic electro-dynamics. Neutrino astrophysics is highly dependent on the nuclear physics results and so on... I'm sure this list could be expanded to almost infinity. So this is not mutually exclusive. It belongs to astrophysics, as it's surely a astronomical observation, but the explanation of the observation wir require a profund understanding of the nuclear physics involved (if any - if you find another explanation from another sector of physics, you're welcome!)
