The Gum Nebula (Gum 12) is an emission nebula that extends across 40° in the southern constellations Vela and Puppis. It lies roughly 400 parsecs from the Earth. Hard to distinguish, it is believed to be the greatly expanded (and still expanding) remains of a supernova that took place about a million years ago. It contains the smaller and younger Vela Supernova Remnant, along with the Vela Pulsar.