Editing Nebula

[[File:Comp-Prog-Dav-R-Deitrick-Starter-Trav-Page-16 16-July-2018a.jpg|right]]
A [[Nebula]] is an interstellar cloud of dust, [[hydrogen]], helium and other ionized gases.
* Nebulae or nebulas can affect [[ship sensor suite]]s or other [[ship equipment]]. 
* They are [[Astrographic Feature]]s.
 
== Description ([[Specifications]]) ==
''[[Wikipedia: Interstellar cloud|Interstellar clouds]]'' are regions of gas, dust, and [[Wikipedia: plasma (physics)|plasma]] that have a higher average density than the general ''[[Wikipedia: Interstellar medium|interstellar medium]]''.  They are typically composed of about 70% hydrogen, the bulk of the remainder being helium with traces of other elements. Nebula can range in size from as small as 1 pc in diameter, as in the case of planetary nebulae, to over 100 pc wide in the case of some of the largest nebular clouds. 
 
=== Basic Nebula Types ===
''[[Wikipedia: Interstellar cloud|Interstellar clouds]]'' can be classified into 3 general types based on the primary form of hydrogen found within:
# ''Neutral Clouds'' ([[Wikipedia: H I region|H I regions]] - formed of atomic hydrogen)
# ''Ionized Clouds'' ([[Wikipedia: H II region|H II regions]] - formed of positively-ionized hydrogen [i.e. "[[Wikipedia: plasma (physics)|Plasma]]"])
# ''[[Wikipedia: Molecular cloud|Molecular Clouds]]'' (Molecular Hydrogen - formed of H<sub>2</sub>)

=== Hydrostatic Equilibrium ===
Under normal circumstances interstellar clouds exist in a state of ''[[Wikipedia: Hydrostatic equilibrium|hydrostatic equilibrium]]'', in which the natural self-gravitation that would otherwise cause the cloud to collapse is balanced by the outward pressure within the cloud due to motion of the atoms and molecules that compose it.  Star formation is normally caused within molecular clouds by a triggering event which locally disturbs this equilibrium, causing runaway local collapsing regions within the cloud.  Such causes can be the collision of one cloud with another, or the shock-wave within the interstellar medium caused by a nearby [[Wikipedia: Supernova|supernova]] explosion.

=== Selected Nebulae ===
* [[Anellet Cloud]]
* [[The Anundarluu|Anundarluu, The]]
* [[Anterior Cloud]]
* [[Basilisk Nebula]]
* [[Beta Niobe Nebula]]
* [[Block Nebula]]
* [[Bourne Cloud]]
* [[The Cauldron]]
* [[Celella Nebula]]
* [[Coalsack Nebula]]
* [[Curtain Nebula]] 
* [[Lesser Curtain Nebula|Curtain Nebula, Lesser]] 
* [[Dark Cloud]]
* [[Deimos Cloud]]
* [[Demon's Eye Nebula]]
* [[Destiabr Nebula]]
* [[Helix Nebula]]
* [[Holowon Cloud]]
* [[Hook Nebula]]
* [[Horsehead Nebula]]
* [[Magister Cloud]]
* [[Inferno Nebula]]
* [[Orion Nebula]]
* [[North American Nebula]]
* [[Pelican Nebula]]
* [[Phobos Cloud]]
* [[Rim Reach Nebula]]
* [[Greater Shell Nebula|Shell Nebula, Greater]]
* [[Lesser Shell Nebula|Shell Nebula, Lesser]]
* [[Separe Cloud]]
* [[Shadow Cloud]]
* [[Spark Nebula]]
* [[Great Ulund Cloud|Ulund Cloud, Great]]
* [[Little Ulund Cloud|Ulund Cloud, Little]]
* [[Veil of The Rim]]
* [[Verant's Head Nebula]]
* [[Wisp Cloud]]

== History & Background ([[Dossier]]) ==
Ancient [[Solomani]] astronomers originally used the [[Latin]] term "[[Nebula]]" (''Lat. "Cloud"'') to refer to any diffuse object observed in the night skies of Ancient [[Terra]]. These included what were termed "nebulous stars" at the time (which included both what were later discovered to be star clusters and nebulae proper) as well as what were later discovered to be galaxies before their true nature was known.  Numerous astronomical catalogs were published by different [[Terran]] observers over a long span of time, which included among their lists objects originally classified as "nebulae". Such catalogs included the ''Messier Catalog'' of Charles Messier (abbr. "'''M'''", which was later supplemented by the the ''Caldwell Catalog'' (abbr. "'''C'''")), and the ''New General Catalog of Nebulae and Clusters of Stars'' (abbr. "'''NGC'''"), with the "''Index Catalog of Nebulae and Clusters of Stars''" (abbr. "'''IC'''") as an associated later supplement, among others.   

* Known to Vilani science 

=== Nebula Effects on Ships ===
Nebulae often interfere with [[sensor]]s, especially commercial [[ship sensor suite]]s. They can affect other [[ship equipment]] as well.{{Unpublished cite|author= Maksim-Smelchak }} Sufficient study by astronomers will allow jumping into and out of the better known nebulae. There is still enough clutter that an [[astrogator]] has to aim for the destination's outer reaches.{{Unpublished cite|author= [[Tom Chlebus]] }} [[Misjump]]s are a strong possibility under many to most conditions.{{Unpublished cite|author= Maksim-Smelchak }} 

''[[Old Spacer's Tale|Old Spacer's Comments]]:'' A nebula is quite impressive from a distance, but usually doesn't look like much close-up. The gas and dust in the typical nebula are actually very sparse, barely more dense than a pure [[vacuum]]. They look impressive from a distance only because they're so deep along our line of sight. Many [[spacer]]s have reported that fuel skimming from a nebula would be about as effective as collecting water by running through fog with a bucket. Under most conditions, it would degrade [[sensor]]s beyond a few dozen [[AU]]. [[NAFAL]] (>0.1c) travel would be hazardous; but it wouldn't ordinarily affect jump nor could it be efficiently skimmed without something like a electro-magnetic [[Ramscoop Jumpship|ramscoop]]. {{Unpublished cite|author= [[William A. Humphrey]] }}
* Note that the term ''dust'' does not generally refer to free-floating silicates or tiny flakes of rock – it is an astronomical term meaning any element that isn't either hydrogen or helium. In the case of nebulae, molecules of elements such as nitrogen or oxygen are ''dust''.

=== Nebula Sizes ===
Nebulae are typically measured in the following units:
{| class="wikitable sortable" 
!colspan="5"|Nebula Size & Location
|-
! Size
! Typical [[Metric]]s
! Remarks
|-
| [[Astrographic Hex]]
| [[Parsec]] or [[AU]]
| These smaller nebulae are typically represented on a single astrographic hex.
|-
| [[Subsector]]
| [[Light-year]] or [[Deshi]]
| They are smaller nebulae by astronomic standards, but less than a subsector in size.
|-
| [[Sector]]
| [[Light-year]] or [[Deshi]]
| These are typical nebulae, often several subsectors in size. Some might be proto-galaxies, failed galaxies, or accreted star clusters... possibly the remants of a nova starburst. 
|-
| Multi-Sector
| [[Light-year]] or [[Deshi]]
| These are truly massive nebulae, often several sectors in size.
|-
|}

== References & Contributors (Sources) ==
{{Intermediate}}
{{Detail}}
{{Sources
|S2= [[Traveller Wiki Editorial Team]]
|S3= Author & Contributor: [[User:WHULorigan|WHULorigan]]
|S4= Author & Contributor: Lord (Marquis) and Master of Sophontology [[User:Maksim-Smelchak|Maksim-Smelchak]] of the [[Ministry of Science]] 
}}


{{LEN|Astrography|Nebula}}