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Daniel Stern

Location of Photo:

Rio Hurtado, Chile

Date/Time of photo:

Various 4/18 - 5/5/23 38 hours




The Pencil Nebula is an emission nebula (clouds of ionized gas that emit their own light, as opposed to reflection nebulae which is a cloud of dust and gas that reflects the light from a nearby star) in the constellation Vela. It’s a small part of a supernova remnant that exploded about 11,000 years ago. The pencil-like shape suggests that it is part of the supernova shockwave that encountered a region of dense gas. It’s that intersection that causes the nebula to glow. The colors of the various regions in the nebula yield clues about this cooling process. Some regions are still so hot that the emission is dominated by ionized oxygen atoms, which glow blue/green in the picture. Other regions have cooled more and are seen emitting red in the image (cooler hydrogen atoms). In this situation, color shows the temperature of the gas.