Largest known emission nebula in terms of how much of the sky it occupies as seen from Earth, extending over about 35k in the southern constellations Puppis and Vela.
A complex of diffuse, glowing gas too faint to see with the unaided eye, it was discovered in the 1950s. It lies roughly 1,000 light-years from Earth and may be the remnant of an ancient supernova .