What is a nebula?

Let's star with the basics. According to Mirriam-Webster, a nebula, or nebulae (plural), is any of numerous clouds of gas or dust in interstellar space. As this definition describes several objects in space, we must categorize them.

Absorption Nebulae

 

Horsehead Nebula
Also known as Dark Nebulae, these super dense clouds block out any light from objects behind them. When looking at a dark nebula, all you can see if the nebula itself, because the light from all objects like stars and such are unable to penetrate through these dense nebulae. Theses clouds are made up of tiny, tiny particles of stellar dust covered in frozen carbon monoxide and nitrogen, which block light very effectively. The only way to see past these clouds is by using infrared technologies or radio waves.

Emission Nebulae


Emission nebulae are made up of a cloud of ionized particles. These particles generally come from a nearby star emitting photons, or particles of light. These photons light up the cloud of ionized particles, making very pretty clouds. Emission nebulae come in several colors, because different ionization energies give off different colors. For example, a nebula with a lot of energy will give off a green or blue color, whereas low energy nebulae will look red.
Tarantula Nebula

Reflection Nebulae



Rho Ophiuchi Complex
Reflection nebulae work kind of like mirrors. When you stand in front of a mirror and turn on a lamp, the mirror reflects your image, and the light coming from the lamp. Reflection nebulae are made up of carbon dust, which has highly reflective properties. This dust  reflects the light coming from other stars, so one could say they amplify the light.

Continue to Subtypes



Project Nebula  ||  The Interstellar Medium  ||  Emission Nebula
Reflection Nebula  ||  The Cosmic Perspective by Bennett, Donahue, Schneider, and Voit