Field guide · Deep sky
NebulaReflection nebula
Dust beside a star that is not hot enough to make gas glow, so the dust simply scatters its light — usually blue, for the same reason the daytime sky is.
- Made of
- Dust grains, lit from outside
- Colour
- Blue, from scattered starlight
- Brightness
- Faint — a photographer’s target
An emission nebula makes its own light. A reflection nebula borrows it. The star next to it is not hot enough to ionise the gas, but the fine dust in the cloud scatters its starlight back towards us like fog around a streetlamp.
Blue light scatters more easily than red, which is also why the daytime sky is blue. So reflection nebulae photograph a soft, smoky blue — the wisps around the Pleiades are the best-known case, and they are not left over from the cluster’s birth: the cluster is drifting through an unrelated cloud.
They are faint and hard to see by eye; a clean optic and a dark sky are what help most, since a filter would dim the starlight they reflect.
See it in the sky
Each one opens the sky map pointed at it, for tonight, from where you are.