Giant Bubble in the Southern Sky

The southern sky contains what must be the largest nebula in our sky, a giant bubble spanning a wide swath of the Milky Way.

This is the object known as the Gum Nebula. You can see it in my previous post, in the ultrawide view of the southern sky. Here I’m framing it with a normal 50mm lens that covers about 50° of sky. The Gum Nebula is completely invisible to the eye and shows up only on photos. It wasn’t even discovered until the 1950s, by Australian astronomer Colin Gum. It is #12 in his catalog of southern sky nebulas. I’ve always thought this was an example of an interstellar bubble, blown by intense winds from hot blue stars, of which there are many in this part of the Milky Way in Vela and Puppis. At left are the four stars of the False Cross in Carina and Vela.

But some sources claim this is a supernova remnant, the blasted remains of a star that blew up 1 to 2 million years ago. It is big because it is close by, just 450 to 1500 light years away depending on what side if the remnant you measure. If that’s the case, the star that exploded would have been quite a shadow-casting sight in our prehistoric sky, assuming it was that close to us when it blew up and was in the night sky at the time.

Either way, it is a great target for amateur photographers, and now with digital cameras it is easy to record. This night, some haze moving through added the photogenic glows around all the stars to bring out their colours.

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