E0102
E0102 , short for 1E 0102.2-7219 , is the remnant of a supernova that exploded in the Small Magellanic Cloud , a neighboring galaxy to the Milky Way . The supernova was caused when a star much more massive than the sun collapsed under its own gravity . The explosion was from the southern hemisphere of the earth have been visible over 1000 years ago. The appearance of E0102 can best be explained by a model in which the ejection is shaped like a cylinder , which is viewed almost closely at the end. This model suggests that the explosion that created the remnant of E0102 might itself have been highly asymmetrical , which is consistent with the quick kicks neutron stars receive after supernova explosions. Another possibility is that the star exploded into a disk of material that formed when material was thrown from the equator of the red giant star in front of the supernova. Such asymmetries have been observed in winds from lower-mass red giants that form planetary nebulae . The remnant consists of an external shock wave created by the supernova and an inner ring of cooler material.This inner ring likely expands the output of the explosion, which is heated by a shock wave that propagates backward into the output. At its center is an isolated neutron star, the first such neutron star to be discovered outside the Milky Way.