Nuclear stars
Neutron stars are the densest objects in the universe and contain a mass equivalent to that of the Sun in a volume about 20 km across. This illustration shows the neutron star 1E1207.4-5209, which was recently found to possess a strong magnetic field (purple lines). Electrons are accelerated by this dipole field and, as a result, emit synchrotron radiation at X-ray wavelengths. Credit: M Weiss.