Caption: Circinus X-1, located in the plane of the Milky Way about 24,000 light years from Earth, is a fledgling supernova remnant and an oddity of the Milky Way. Known as an X-ray binary system, Circinus X-1 contains a neutron star, the dense cinder of the exploded star, a companion star and the glowing nebula of ionized gas that is the hallmark of a massive supernova explosion.