Nebulae
Nebulae are giant clouds of dust and gas. Stars form inside of them. If they were not there you could read a book by the light of the stars.
All nebulae are a spectacular sight in the night sky, but the most colorful and beautiful is the emission nebulae.
There are four different types of nebulae, emission, reflection, dark, and planetary. Early astronamers thought that planetary nebulae looked like Uranus and Neptune which is why they are called planetary nebulae. Now we know they don't have anything to do with planets.
Reflection nebulae are lit up by the light
of nearby stars reflecting off of them. They appear blue because the dust grains scatter the light around.
Dark nebulae appear dark because there are no stars around to light them up. They can only be spotted because they block out the light from far away stars.
Nebulae such as the Crab nebula are
remnants of a supernovae. Supernovae remnant nebulae often look messy and torn. This is because the force of the exploding star scattered the dust and gas.
