In my second book, I mention the “Gum Nebula” several times. It’s something of a landmark (or should I say, “space mark”?) being that it is near a spot where the Orion arm splits into two, and it is fictionally near the boundary to Dakh Hhargashian space.
The Gum Nebula was discovered by a guy named Colin S. Gum, PhD. He was one of Australia’s top astronomers, and he died in a skiing accident at the age of 36. Still, in that short amount of time, he cataloged 85 different nebulae in the southern sky. They are all listed as Gum 1, Gum 2, Gum 3, etc. But when people speak of the Gum Nebula, they are usually referring to Gum 12. (Many other nebulae in the Gum catalog also have other names, like the Seagull Nebula or Thor’s Helmet.)
The Nebula itself is so diffuse you can’t see it with the naked eye. And, at least from Earth, it is the largest nebula in the sky. At 1,300 lightyears distance from the earth, the nebula is about 1,000 lightyears across. The gas within the nebula is excited by two different stars, which cause the hydrogen gas in the nebula to glow.