Gum Nebula - A very large, near-circular emission nebula, approximately 36◦ in diameter, in the constellations Puppis and Vela. The largest known nebula in the sky, it was discovered by the Australian astronomer C S Gum (1924–60), and is believed to be an ancient supernova remnant, with an age exceeding a million years. It is a convoluted mass of nebular wisps and loops, many of them very faint, but there are also numerous brighter parts. Its distance has been estimated at 1300 light-years, indicating that the nebulosity is approximately 840 light-years across. Within one of its brightest regions both the brightest-known Otype star ζ Puppis (spectral type O5f) and the brightest Wolf–Rayet star γ 2 Velorum (type WC8), are found. The much more recent Vela pulsar and supernova remnant also lie within the Gum Nebula, which for many years has rivalled the Crab Nebula in interest for astrophysicists.
