=^= 0.3.3 - Nebula Classification

Created by Captain Lirha Saalm on 26 Jul 2013 @ 9:35am

Introduction to Nebulae

Nebulae are extremely large interstellar clouds which contain a variety of ionized gasses, dust, hydrogen, helium, plasma, and other elements. They are found throughout the Milky Way galaxy and come in many different shapes and sizes, and contain different properties according to their specialized classification. The high concentration of stellar matter (dust, gas, etc.) present within these nebulae tend to naturally clump and stick together which eventually leads to the formation of celestial bodies over periods of millions of years. As such, nebulae are often considered to be 'stellar nurseries' - places where planets, comets, asteroids, and (most importantly) stars can form. They are essentially prime real estate for the building blocks of known stellar matter.

Below are the various main classifications for different types of nebula. In addition to the main classification, many nebulae contain one or more sub-classifications, usually according to their unique locations and individual properties. For example, a Class A emission nebula might be a standard one of its type, or it may possibly a Class A Type 2 (Disruptive) nebula which contains additional properties which interfere with certain biological and/or technological functions. Just like humans, each nebula in the universe is different, and it is important to understand and analyze these cosmic clouds as we explore the galaxy.

Class A - Emission

Class A nebulae are referred to as Emission nebulae. They are generally the largest type of nebula, usually spanning 100 to 5,000 light years in diameter, and can be visually identified from over a sector away. These nebulae are often so large because they usually contain a Class B H II Region nebula within, which is a smaller and more condensed cloud where star formation typically occurs. Emission nebulae tend to linger between one and two million years before they dissipate, and have an average temperature of 10-20 K. Containing a mixture of green, red, and blue coloring, Class As are mainly composed of hydrogen, helium, and oxygen, and are called 'emission' nebulae due to their high concentrations of plasma which are similar to that emitted by modern-day starships.

Class B - H II Region

Class B nebulae are commonly referred to as H II Regions. H II Regions are usually found within Class A Emission nebulae, and are primarily made of high concentrations of hydrogen and helium - the building blocks of star formation. As such, Class B nebulae are considered to be stellar nurseries, and these types of nebula can birth thousands of stars over their lifespan of one to two million years. Red and pink in coloration with a hot average temperature of around 10,000 K, H II Regions are usually 20 to 2,000 light years in diameter.

Class C - Bok Globule

Small, dense, and compact, Class C nebulae are the densest type of stellar cloud and are ideal for star formation due to their extreme concentrations of hydrogen, helium, and carbon. Spanning only a light year or two in diameter and only lasting one or two million years, Bok Globule nebulae are where the majority of binary and trinary star systems form. The average temperature in a Class C is relatively tame, only about 3 K, and their coloration is usually dark gray or black, making them difficult to detect with the naked eye.

Class D - Reflection Nebula

Class D Reflection nebulae are the longest-living nebulae known to exist, with the average lifespan being anywhere between 10 million and 10 billion years. Their name derives from their reflective properties which are a result of large concentrations of dust and other reflective material such as iron, nickel. Hydrogen and carbon are also present but although star formation can occur within Class D nebulae, it is more common to see nearby stars being brilliantly reflected within the nebula. Reflection nebulae are usually blue, cyan, and purple in hue, and have a high temperature of 25,000 K due to the heavy amounts of dust present which are able to trap and retain heat.

Class E - Planetary Nebula

Class E nebulae are bright orange, green, and blue clouds of matter which form during the final stages of a star's life. Despite their name, they have virtually nothing to do with planets, but rather are created when a star loses its ability to maintain nuclear fusion. The degradation of this energy reaction expels gas and stellar matter into space around the star, which ultimately creates the nebula itself. Planetary Nebulae are short-lived and only last about 10,000 years. They are also very small and no bigger than one light year in diameter, yet due to their close proximity to the failing star, they are hot with an average temperature of around 10,000 K. They are composed of primarily of carbon, nitrogen, oxygen, and calcium.

Class F - Dark Nebula

Possessing very strong magnetic fields and virtually impossible to visually identify against the black backdrop of space, Class F nebulae are appropriately named 'Dark Nebulae' due to their deep black color. They are generally larger-sized nebulae which span about two hundred light years across, and are composed primarily of hydrogen. The average temperature of a Class F nebula is only about 7 K, however they are very dense and can pose significant navigational problems for nearby starships due to the high gravimetric forces which result from the cloud's microwave (EM) radiation.

Class G - Supernova Remnant

One of the most awe-inspiring types of nebulae known to exist, Class G nebula are bright orange and blue-colored clouds which are the remains of a giant star. These Supernova Nebulae consist of ionized hydrogen and oxygen which are the leftovers of a star's implosion process. Extremely hot in temperature - up to 10 million K - and lasting up to one million years, these colorful clouds are usually one to three light years in diameter, depending on the size of the star which went supernova.

Class H - Nova Remnant

A Class H Nova Remnant nebula is the little sister of the larger Class G Supernova Remnant. Virtually identical in color and composition yet smaller in scale, Class H clouds are produced when a star's fusion process fails and goes nova. They do not last long, only about three hundred years, and are only half a light year in diameter. They are also much more common than Class G nebulae and are substantially cooler, only about 5,000 K. Composed of ionized hydrogen and oxygen, they vary in color but are usually identifiable by their orange and blue hues.

Class I - Solar Nebula

Class I nebulae are commonly referred to as 'Solar Nebulae' because they are very small clouds where young stars and their solar systems form. Solar nebulae are typically only 100 AU in diameter and are created when a new star's gravimetric forces pull and attract stellar debris around itself. This debris eventually clumps and mashes together within the Class I nebula, leading to the formation of celestial bodies such as planets, comets, asteroids, and moons. They are composed of hydrogen, helium, and oxygen, and last about two million years. Their coloration is usually yellowish-orange, and the average temperature within the nebula is around 150 K.

Class J - Wolf-Rayet Nebula

Class J Wolf-Rayet Nebulae are unique to Spectral Class O stars, and form when an occasional strong stellar wind depletes the star's mass. The high winds blast the star's core materials away, which are then recaptured by the star's gravity to form a large halo-like cloud around the star. They are small in size, only half a light year, and are composed of the same materials as the star - helium, oxygen, and carbon. Bright blue in color similar to all Spectral Class O stars, these nebulae last approximately one to two million years and have an average temperature of 25,000 to 50,000 K.

Class K - Inversion Nebula

Class K Inversion Nebulae are extremely rare and very unstable. They are formed by highly-concentrated strings of plasma and only last for a few years, usually five to ten before the plasma dissipates into space. They are also very small, about 200 AU which is slightly bigger than a solar nebula. Bright pink in color, they have an average temperature of 10,000 K.

Sub-Classifications

• Type 1 - Protomatter: a nebula which contains large amounts of protomatter, a highly dangerous and unstable form of matter.

• Type 2 - Disruptive: a nebula which contains high amounts of EM (microwave) radiation and can interfere with technological and biological properties.

• Type 9 - Shadow: an extremely dense nebula composed of elements which produce sensor shadows, also known as 'sensor ghosts'. With prolonged exposure, shadow nebulae are also very dangerous and disruptive to humanoids' nervous system.

• Type 10 - Deuterium: a nebula which contains high amounts of deuterium (heavy hydrogen). Most starships are able to collect deuterium and convert it into fuel using bussard collectors, which makes these types of nebulae ideal for replenishing impulse and warp core reserves.

• Type 11 - Argon: a nebula which contains amounts of argon. Other elements are also present, including thetazenon, fluorine, and sirillium.

• Type 13 - Mutara: a nebula containing ionized gasses which, due to its unique properties, contains high amounts of static discharge. This static discharge is known to severely interfere with a starship's systems, and often causes shields and sensors to become severely degraded, if not completely inoperable.

• Type 16 - Protostellar: a nebula which is in its early stages of formation. Due to the changing and formative nature of the nebula, it often contains many pockets where matter is in a state of particle flux.

• Type 17 - Sirillium: a nebula which contains high amounts of sirillium, an extremely volatile element which can be ignited by common energy weapons.

(Created by Lirha Saalm, USS Galileo; Source: Star Trek: The Final Frontier - Nebula Classification)