Supernova Remnants = Formed after very large stars that have exploded at the end of their life. Ex: Cat's Eye Nebula, Hourglass Nebula, Helix Nebula, Eskimo Nebula. Planetary = formed from star that was probably around the size of our own sun underwent the final stages of its life shedding its outer shell of gasses. Ex: Rectangle Nebula, Oyster Nebula, Westbrook Nebula. The star will continue to feed of the hydrogen envolope until it reaches a certain temperature at which it will ionize the gasses in the nebula and transforms into an Emmission Nebula. Protoplanetary = a gas cloud containng one or more infant stars fromed from a hydrogen envolope, this young star sizzling at around 5,000 K produces strong winds that shape the nebula. There are many varieties of nebula out there.
