The Cygnus Loop is a massive supernova remnant (SNR) located about 2,600 light years away from Earth. Being nearly 3 degrees wide, the nebula is roughly 6 times larger than the full moon. This translates to the nebula being about 120 light years in diameter. Interestingly, searches for the remains of the star that caused this SNR have yet to bear fruit, and the remanent is possibly a neutron star.