Nebulae

From Memory-Zeta

There are many nebulae classified by Starfleet. Here are the most common.

[edit] Primary Nebula Classes

**Emission Nebula - Class A**
Composition	Hydrogen, helium, oxygen
Average Size	100 - 5,000 ly
Average Temp.	10 - 20 K
Lifespan	1 - 2 million years
Color	Red, green, blue
Example	Lagoon Nebula, Veil Nebula, Krai’jih’na Nebula
Pictured	Orion Nebula (M 42)

Emission nebulas are large clouds of ionized plasma where star formation usually takes place. They are illuminated from within by groups of young stars that form in H II Regions within the nebula.

**H II Region - Class B**
Composition	Hydrogen, helium
Average Size	20 - 2,000 ly
Average Temp.	10,000 K
Lifespan	1 - 2 million years
Color	Red, pink
Example	Eagle Nebula, Cone Nebula
Pictured	Tarantula Nebula (NGC 2070)

An H II region is a large stellar nursery, typically located inside an emission nebula. Over the duration of its lifespan, an H II region can give birth to thousands of stars. Gravimetric forces by the larger stars will eventually disperse the nebula and leave behind a star cluster similar to the Pleiades.

**Bok Globule - Class C**
Composition	Hydrogen, helium, carbon
Average Size	1 ly
Average Temp.	3 K
Lifespan	1 - 2 million years
Color	Black
Example	NGC 1999, IC 2944
Pictured	NGC 281

While an H II region can span light years and contain dozens of stars in varying states of development, Bok Globules are dense clusters of dust and gas where star formation actually takes place. They commonly result in binary and trinary star systems.

**Reflection Nebula - Class D**
Composition	Hydrogen, carbon, iron, nickel
Average Size	100 ly
Average Temp.	25,000 K
Lifespan	10 million - 10 billion years
Color	Blue, purple
Example	Trifid Nebula, Witchhead Nebula
Pictured	Pleiades Cluster (M 45)

Reflection nebulas are large clouds of dust that reflect light from nearby stars. The nearby stars are not usually hot enough to cause ionization, but are bright enough to make the dust visible. Star formation can occur within a reflection nebula.

**Planetary Nebula - Class E**
Composition	Carbon,oxygen,nitrogen,calcium
Average Size	1 ly
Average Temp.	10,000 K
Lifespan	10,000 years
Color	Orange, green, blue
Example	Ring Nebula, Hourglass Nebula, Cat's Eye Nebula
Pictured	Helix Nebula (NGC 7293)

Despite the name, planetary nebulas have nothing to do with planets. They are, in fact, the final stage of life for most stars, developing when a star is no longer able to sustain nuclear fusion. As the star’s core contracts, it ejects ionized gases into space, creating a planetary nebula. This plays a crucial role in the evolution of the galaxy, for the process returns material to the interstellar medium.

**Dark Nebula - Class F**
Composition	Hydrogen
Average Size	200 ly
Average Temp.	7 K
Lifespan	1 - 2 million years
Color	Black
Example	Coalsack Nebula, Snake Nebula
Pictured	Horsehead Nebula

Dark nebulas are a type of large molecular cloud. The cloud cores are completely invisible to the naked eye, and are be undetectable aside from microwave emissions from the molecules within. Dark nebulas have strong magnetic fields that create considerable gravimetric forces in and around the nebula. Stars and astrophysical masers can form deep inside dark nebulas. They are named such because from Earth they seem to be blocking the light coming from behind them, appearing dark.

**Supernova remnants - Class G**
Composition	Ionized hydrogen, oxygen
Average Size	3 ly
Average Temp.	10,000,000 K
Lifespan	1,000,000 years
Color	Varies; typically orange, blue
Example	Tycho's Remnant,1987A
Pictured	Crab Nebula (M 1, NGC 1952)

When a massive star reaches the end of its life, it explodes in an immensely powerful supernova. This event blows the entire star apart, leaving in its wake a remnant nebula that expands into the interstellar medium.

**Nova Remnants - Class H**
Composition	Ionized hydrogen, oxygen
Average Size	0.5 ly
Average Temp.	5,000 K
Lifespan	300 years
Color	Varies; typically blue, orange
Example	RR Pictoris, T Pyxidis
Pictured

Nova remnants are similar to supernova remnants, only much smaller on all levels. They are also much more common.

**Solar Nebula - Class I**
Composition	Hydrogen, helium, oxygen
Average Size	100 AU
Average Temp.	150 K
Lifespan	2,000,000 years
Color	Yellow, orange
Example	Panak
Pictured	Artist's Depiction

While most stars form within emission nebulas, there are exceptions to the rule. When a young star forms elsewhere, gravimetric forces gradually attract a disk of dust and gas that flatten to form a new star system that includes planets and asteroids.

**Wolf-Rayet Nebula - Class J**
Composition	Helium, carbon, oxygen
Average Size	0.5 ly
Average Temp.	25,000 - 50,000 K
Lifespan	1 - 2 million years
Color	Blue
Example	NGC 6888, NGC 3199, Gamma Velorum
Pictured	Artist's Depiction

A Wolf-Rayet nebula forms when strong stellar winds cause a Class O star to rapidly lose its mass. The dispersed mass forms a nebulous halo around the star.

**Inversion Nebula - Class K**
Composition	Ionized plasma strings
Average Size	200 AU
Average Temp.	10,000 K
Lifespan	5 - 10 years
Color	Pink
Example	Lukkaris Nebula
Pictured	Marayna's Nebula

Inversion nebulas are rare, highly unstable nebulas created by plasma strings. They typically burn out after a few years.

[edit] Additional Nebula Subclasses

Protomatter
A nebula that contains amounts of protomatter.

Disruptive
A nebula that contains disruptive electromagnetic radiation.

Shadow
An ultra-dense nebula with constituent compounds that create sensor shadows. Prolonged exposure is detrimental to humanoid nervous systems.

Deuterium
A nebula that contains deuterium.

Argon
A nebula that contains argon. Thetazenon, fluorine, and sirillium can also be present.

Mutara
A nebula that contains high levels of static discharge and ionized gases; renders shields and sensors inoperable.

Protostellar
A nebula still in its formative stages. Has high levels of particle flux.

Sirillium
A nebula that contains amounts of sirillium.

[edit] References

http://www.sttff.net/ast/AST_nebulaclassification.html

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