Many types of nebulae exist, but most of them fall under the broader category of diffuse nebulae. The term diffuse nebula merely means that the nebula is irregular and has no exact edge or boundary. Diffuse nebulae are divided into subcategories based on how they are visible.
- Emission Nebula: A nebula that is visible due to the ionized Hydrogen and Helium within it
- Reflection Nebula: A nebula that reflects the light of a nearby star
- Dark Nebula: A nebula that would normally be invisible, but is illuminated by a star behind it.
Nebulae are among the most beautiful objects in the Universe.
The Helix Nebula.
The famous Pillars of Creation seen in the Eagle Nebula.