Medusa Nebula (HSO)

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Planetary Nebulae seem to come in all shorts of shapes and sometimes it can be hard for astronomers to be certain exactly what a particular blob of gas is. This one was discovered by George Abell in 1955 and he classified it as a planetary nebula but then astronomers through it was a supernova remnant. Then in the early 1970’s radio astronomers decided it was most likely a planetary nebula based on its expansion rate. But note that “most likely”. I don’t know what the degree of certainty is but this is one of those nebulae that make it clear that it isn’t always obvious what we are seeing. Certainly I can see why some astronomers thought it might have been a supernova remnant.

Whatever it is, it’s a fascinating nebula! But it is also faint. This is 32 hours of data and more would have been welcome though in our case column defects on the sensor probably place an effective upper limit on how deep we can go on an image.

This nebula is in Gemini near the border of Canis Minor. It’s about 1,500 light years away. The nebula’s apparent size (like most planetary nebulae) is fairly small at only 10 arc minutes (about ⅓ the diameter of the full moon).

You can find the technical details at astrobin.

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