GalaxiesGalactic Dust and Nebulae |
How many kinds of nebulae are there? |
There are numerous kinds of nebulae, which bear informal as well as formal names. Generally, types of nebulae are described either by their appearance (for example, dark nebulae, reflection nebulae, and planetary nebulae) or the physical processes that create them (such as protostellar nebulae, protoplanetary nebulae, or supernova remnants).