Happy Easter, from approximately 3000 light years away! This is the Egg Nebula, and with a length of roughly a light year, it’s the largest Easter egg you’ll ever see!
The Egg (RAFGL 2688) is probably one of my favourite nebulae. It’s a rare pre-planetary nebula*, which means when you look at this thing, you’re actually looking at a dying star shedding its outer layers. When stars do this, they tend to blast away layers of gas in little puffs, which is what causes those ripples you can see throughout the object.
(I say little… They’re little compared to the star, but each puff probably contains enough material to make a few thousand Earths!)
As anyone who reads my blog regularly may know by now, some of that hot gas being cast off by this start will start to condense quite rapidly into dust. You can see it in the picture, it’s that dark band right in the centre, blocking any direct light from the star. Those two strange looking beams are actually starlight shining through regions where there’s less dust. We can see the beams, because they’re illuminating yet more gas and dust further out. In a sense, they’re gargantuan sunbeams!
Actually, all that dust is also the reason for the colours in this image. Because those dust grains are actually tiny crystals, they reflect light in specific ways — They polarise the light. This picture was taken with, effectively, a polaroid filter, and the colours show which directions the light is polarised in. Which, in my humble opinion, is pretty cool.
Preplanetary nebulae are also pretty damn fascinating, astrochemically speaking, what with all of that hot stellar material combining into dust and molecules. The spectrum of an object like this always shows some unusual absorbtions and emissions (especially in the infrared). The Egg, in particular, is known to show some infrared signatures of those delicious** PAHs I keep rambling about…
*Incidentally, these objects should be more properly called “protoplanetary nebulae”. I don’t like the term though, to be honest, seeing as “protoplanetary” makes people think of planet formation. Explaining the difference between a proto-planetary nebula and a protoplanetary disk just becomes tedious, so I prefer “preplanetary nebula”. Seemingly, I’m not alone, either…
**I say ‘delicious’, but ‘horribly carcinogenic’ would probably be more accurate.