Emission and reflection nebulae are both types of nebulae, but they differ in several key aspects:
-
Hard Line Edges:
- Emission Nebulae: These can often have soft, diffuse edges, as the glow results from gas being ionized by young, hot stars, leading to a more spread-out appearance.
- Reflection Nebulae: These may have sharper outlines because they reflect light from nearby stars, and the boundaries can appear more defined, although they can also be diffuse depending on the density of the dust.
-
The Presence of Young Stars:
- Emission Nebulae: Typically associated with very young, hot stars (O-type and B-type stars) that emit a lot of ultraviolet light, which ionizes the surrounding gas and causes it to glow.
- Reflection Nebulae: Often associated with younger stars as well, but the stars are not necessarily as hot or bright as those found in emission nebulae. The light from the stars is scattered rather than ionizing the gas.
-
Contain Remnants of Stars:
- Emission Nebulae: May contain remnants of stars, particularly in cases where supernova remnants ionize the surrounding gas, creating bright emission features.
- Reflection Nebulae: Typically do not contain remnants of stars but rather consist of dust and gas that reflects the light of nearby stars.
-
Interactions with Light:
- Emission Nebulae: The light is primarily a result of the gas ionizing due to nearby stars, which means they primarily emit their own light.
- Reflection Nebulae: The light is reflected from nearby stars; they do not emit their own light but instead illuminate the surrounding dust and gas.
In summary, the main differences lie in their luminescence (ionized vs. reflected light), the type of stars associated with them, and their overall nature regarding edges and structures.