Geminga is the nearest and most famous neutron star. It is only 500 light years away from Earth. It is extremely small and dense: its radius is only 10 Km, and it has the same mass as the Sun. It spins around its axis in a quarter of a second.

The bright tails behind Geminga, detected in 2004 by EPIC camera, are trails of charged particles ejected by the magnetic poles of the star.