Star Trek Stellar Cartography

by Wm. Robert Johnston
June 1999 with minor updates 10 September 2001
(under construction)


  I. Introduction
      A. Preface
      B. Sources
      C. Organization
      D. Units
 II. The Milky Way Galaxy
      A. General information
      B. Issues with the Star Trek galaxy
      C. Territorial holdings in the Star Trek galaxy
III. Stars
      A. Pre 22nd-century star designations
      B. Star Trek star names
 IV. Planets
      A. Star Trek planet classes
      B. Terms
      C. Known planet classes
      D. Planet placement

Appendix A: Astronomy background information

I. Introduction

I. A. Preface

The issue of defining elements of stellar cartography in the Star Trek universe is a thorny one, to say the least. After all, the adopted conversions for warp factor to actual speed is still short by a factor of 10 to 1,000 of speeds implied by travel within and between episodes. Star Trek producers have become meticulous about historical consistency, have improved the consistency of stardates, but continue to ignore galactic astronomy and geography. Nonetheless, we can discern some information from Star Trek canon. This paper will review various elements of cartography in the Star Trek universe and related topics in relation to current astronomical knowledge.

I. B. Sources

This paper will consider principally those sources generally considered Star Trek canon. This includes: all Star Trek television series episodes (TOS, TNG, DS9, and VGR) and motion pictures and the recent encyclopedic publications of the Star Trek producers (Star Trek Encyclopedia, Star Trek Chronology, Star Trek: The Next Generation Technical Manual, and Star Trek: Deep Space Nine Technical Manual). Some "noncanonical" sources provide gap-filling information and are semi-authoritative and will be cited periodically; such information will be indicated as such.

One of the best compilations of canonical information is that of D. Joseph Creighton on his web page Star Trek Archive, including "Star Trek Locations."

I. C. Organization

This discussion will cover a variety of topics in the field of astronomy: galactic astronomy, stellar astronomy, stellar evolution, positional astronomy, planetary astronomy, historical astronomy, and so on. Given that some readers are better grounded than others in these topics, I have attempted to, as appropriate, remove the information which is background on astronomy to appendix A. Readers interested in explanations may refer to this as needed.

I. D. Units

Some units that will be used here:

AU or astronomical unit: 1 AU = the average Earth-Sun distance, or 149,600,000 km. This is more convenient for expressing distances within a planetary system to avoid unwieldy numbers and to facilitate comparisons to our own Solar System.

ly or light year: 1 ly = the distance traveled by light in vacuum in one year, or 9,460,000,000,000 km. This is more convenient for expressing distances between stars and across the galaxy--again, we avoid unwieldy numbers and facilitate comparisons to distances traveled at warp speed.

km or kilometer: If you don't know metric, it's time to learn.

MJ or mass of Jupiter, and ME or mass of Earth: masses of planetary objects are easier to express and compare in terms of these representative planets. Earth's mass is 5.988 x 1024 kg, and Jupiter's mass is 317.84 times as much.

II. The Milky Way Galaxy

II. A. General information

The Sun and the UFP are located in the disk of a spiral galaxy, the Milky Way Galaxy. The flat disk of spiral arms is about 70,000 light years in diameter; the central core is about 20,000 light years in diameter. The Sun is located 28,000 light years from the center and 65 light years above the central plane of the disk.

Astronomers have some information about galactic cartography for this side of the galaxy (Alpha and Beta quadrants) and very little for the far side (Delta and Gamma quadrants).

The coordinate system used below adopts as (0, 0, 0) a point in the galactic plane below the Sun system. This makes the Sun's coordinates (0, 0, 65) in light years. The positive X-axis is directed into the Alpha quadrant; the positive Y-axis is directed to the galactic center.

II. B. Issues with the Star Trek galaxy

How large is Federation space? Trying to answer this question brings on many of the cartographic contradictions of Star Trek. Some relevant data:

II. C. Territorial holdings in the Star Trek galaxy

Other difficulties involve the layout of Federation space with respect to the various hostile and semi-hostile empires. The worlds that became the Federation encountered the Romulans before 2160; the Klingons in 2218; the Cardassians by 2350; and the Ferengi before 2364.

III. Stars

A number of real stars and objects have turned up in Star Trek, suggesting some cartographic information. First some review of stellar designations.

III. A. Pre 22nd-century star designations

Many systems of stellar designations exist, resulting in multiple "names" for a given star. Some stars (generally bright ones) have been named since antiquity. Examples include Sirius, Betelgeuse, and Polaris. A few stars have received such names in modern times; Barnard's Star is an example.

In the 1800s the brightest stars in each constellation were given designations using successive Greek letters (for successively dimmer stars, starting with the brightest) and the constellation name. Examples include Alpha Centauri and Epsilon Eridani. Sirius is thus also Alpha Canis Majoris. Later numbers and constellation names were combined for designations.

In the 1800s and 1900s astronomers produced a wide variety of catalogues of stars (and other objects). These each independently assign designations to included stars. Some include all stars in the sky (or a certain portion of the sky) down to a certain cutoff brightness, while some only include stars of special interest (only multiple stars, only variable stars, only white dwarf stars, only stars with apparently large background motion, etc.). One example is Wolf 359, star number 359 in Wolf's catalog, also site of the battle with the Borg in year 2367.

Thus, a given star may have many names. The nearest star system to the Sun is a multiple star Alpha Centauri (brightest star in the constellation Centarus), also known as Rigel Kentauris (name given by navigators), or HD 128620 and HD 128621 (in the Henry Draper catalog), or SAO 252838 (in the Smithsonian Astronomical Observatory catalog).

III. B. Star Trek star names

In Star Trek stars (or star systems) may be referred to by name, or planets may be referred to by name. The convention linking these in most cases is given the star's name (Sigma Iota), planets are designated by successive Roman numerals in order of distance from the central star (Sigma Iota I, Sigma Iota II, and so on). Some inconsistencies with this system occurred in TOS, but the convention is now fairly established. This convention will be adopted here and be used to link star systems and planet names.

Many stars and systems named in Star Trek have used actual (21st century) star names. This has produced some problems. As mentioned earlier, some stars have multiple names or designations. In Star Trek different episodes have employed alternate names for the same star--an example being Alpha Leonis (TNG "The Vengeance Factor") and Regulus (TOS "Amok Time").

Another problem is that the same name has been used for planets which may or may not be in the same system. The best example here is Rigel. Rigel is a B-type star about 41,000 times as luminous as the Sun--not the type of star likely to possess habitable planets. Nonetheless, various episodes have referred to Rigel III (TNG "All Good Things..."), Rigel IV (TOS "Wolf in the Fold"), Rigel V (TOS "Journey to Babel"), Rigel VII (TOS "The Cage"), and Rigel XII (TOS "Mudd's Women"). The Technical Manuals indicate that by 2370 major Star Fleet production facilities are located at Rigel IV and Rigel VI. Even worse, Rigel XII is indicated in "Mudd's Women" to be isolated, necessitating the USS Enterprise's visit.

Nonetheless, making the assumption that a star or system mentioned in Star Trek that has the same name as a star known to us today is, in fact, that star allows us to develop some cartographic information.

Table 1 lists the 30 such stars along with their three-dimensional location in the galaxy, using the coordinate system discussed below.

A review of this information indentifies some problems. The listed stars include sites of exploration by the crew of the Enterprise and Enterprise-D, implying that they are on the frontiers of Federation space. However, all but two of the stars are within 420 ly of Earth, and half are within 80 ly of Earth. This is a tiny fraction of the volume of Federation space implied by Captain Picard's statement in ST: Generations that the Federation spans 12,000 ly.

Table 1: Star Trek stars with known locations

starepisodeX (ly)Y (ly)Z (ly)
AcamarTNG The Vengeance Factor -48 64 85
AldebaranTOS Where No Man Has Gone Before; DS9 Past Tense Part I 1 -61 42
Alpha CarinaeTOS Wolf in the Fold 279 -43 -69
Alpha CentauriTOS Metamorphosis 3 3 65
Alpha Eradani (Aradoni?)TOS Wolf in the Fold 70 27 -58
AltairTOS Amok Time; TNG Encounter at Farpoint -12 11 62
Atria (Atrea?)TNG Inheritance 249 314 -44
Beta AurigaeTOS Turnabout Intruder -18 -79 80
CapellaTOS Friday's Child -13 -40 68
Cor Carloi (Corcoroli?)TNG Allegiance -19 10 173
DenebTOS Wolf in the Fold; TOS I, Mudd; TNG Encounter at Farpoint-2160 220 140
Epsilon HydraDS9 Q-Less 77 -90 130
Epsilon IndiTOS The Enemy Within 3 7 56
Gamma Eridani (Eradon?)TNG Redemption II 67 -143 -90
Gamma HydraTOS The Deadly Years; TNG The Vengeance Factor 77 67 149
Gamma TauriTNG The Last Outpost -2 -141 3
Gamma TrianguliTOS The Apple -64 -84 14
Groombridge 273ST:DS9 Technical Manual
MerakTOS The Cloudminders -23 -39 130
Mira/Omicron CetiTOS This Side of Paradise; TNG Conspiracy -47 -217 -290
MizarTNG Allegiance -34 -15 134
Omega SagittaTNG The Outrageous Okona -18 68 32
PolluxTOS Who Mourns for Adonais? 7 -30 78
Regulus/Alpha LeonisTNG The Vengeance Factor 37 -35 123
RigelTOS The Doomsday Machine; TNG All Good Things...; TOS Wolf in the Fold; TOS Journey to Babel; TOS The Cage; TOS Mudd's Women 340 -610 -260
Sigma DraconisTOS Spock's Brain -17 -3 72
Sun/SolEarth's primary 0 0 65
Tau CetiTNG Conspiracy 0 -3 54
Tau CygnaTNG The Ensigns of Command -67 8 56
VegaTOS Mirror, Mirror -22 9 73
Velara/Pleiades ClusterTNG Home Soil -86 -338 -87
Wolf 359TNG The Best of Both Worlds 4 -2 71

Table 2: Other stars of significance

starsignificanceX (ly)Y (ly)Z (ly)
40 Omicron 2 Eridani AVulcan primary? 4 -12 55
Epsilon EridaniVulcan primary? 2 -7 57
Proxima Centaurinearest star to Sun 3 3 65
PSR 1257+12pulsar with planets 190 160 1010
PSR B1620-26pulsar with planets 890 5580 1680
Siriusbrightest star from Earth 6 -6 64

III. C. Presumed locations of Star Trek systems

We can now apply the above information to give coordinates for locations unique to Star Trek.

IV. Planets

IV. A. Star Trek planet classes

Star Trek employs a planetary classification system, summarized in Table 3 (as so far described in canonical sources). It appears that this not a true planetary classification system but a planetary atmosphere classification system. First, several classes are suitable for unprotected breathing (classes L and M) or nearly so (classes H, K, and N). All of these are listed as classes of environments for Galaxy-class starships in the ST:TNG Technical Manual. Second, the use of single letters implies a relatively small number of classes. However, planets where humans can breath are a tiny fraction of possible planetary environments--but they are a significant fraction of those of dramatic interest to Federation visitation. Third, single classes have included a broad range of sub-stellar objects: Class-M has been applied to planets like Earth and to asteroids. These are very different objects astronomically, but as shown by the lack of asphixiated crew members share a breathable atmosphere. The best explanation is that these classes identify the nature of the atmosphere.

Table 3: Star Trek planet classifications

Class-Dsmall, rocky planetoid
Class-Hgenerally extremely dry, sometimes habitable; breathable?
Class-Jgas giant
Class-Kuninhabitable environment but terrestrial gravity; breathable?
Class-Lsmall, rocky terrestrial planet with O2-Ar atmosphere
Class-MEarth-like planet with O2-N2 atmosphere
Class-Nenvironment for some Federation species

IV. B. Terms

Before going further, several terms need to be defined. Planets are large objects orbiting a star. Brown dwarfs are intermediate between stars and planets. Moons are objects orbiting a planet or asteroid. (The term "moon" will be used here instead of "natural satellite".) Smaller objects orbiting a star may be called asteroids, planetoids, comets, meteroids, etc.--notice we didn't say what "large" is? The size-based distincts will prove somewhat arbitrary. Star Trek occasionally uses the term planetoid. This term isn't much used in modern astronomy; "planetesimal" is the closest and refers to the objects which accrete into planets when a planetary system is forming. The smallest planet in our Solar System, Pluto, is 2,300 km in diameter; the largest rocky asteroid, Ceres, is 1,000 km in diameter. The largest known icy asteroid or trans-Neptunian object, 2001 KW76, is 1,200 km in diameter. The largest moons (Ganymede of Jupiter and Titan of Saturn) are larger than two planets (Mercury and Pluto). Any planetary classification scheme will have to apply to moons as well and will need some semi-arbitrary size limits.

IV. C. Known planet classes

Astronomers in our century have examined only a small sample of planets: those in our own Solar System. The three dozen planets discovered to date orbiting other stars have all been detected indirectly. We have extremely little information on these objects--but that has been enough to upset the standard ideas about what types of planets there are. (Such is the nature--and excitement!--of science.) Current observational and theoretical astronomical knowledge suggests the following general catagories of sub-stellar bodies:

brown dwarfs: these objects are intermediate between stars and planets and have masses ranging from 11 J to 80 J (3,500 E to 25,000 E). Diameters range from 300,000 km to 1,300,000 km during deuterium burning and from 100,000 km to 200,000 km when mature. They were too small to sustain hydrogen fusion and thus become stars, but large enough to briefly sustain deuterium fusion. They are also distinguished from planets in composition, being like stars in amounts of heavy elements.

Jovian planets: this term is here applied to massive planets with thick atmospheres of hydrogen and interiors including metallic hydrogen. Masses range from 40 E to 3,500 E (0.13 J to 11 J); diameters range from 80,000 km to 250,000 km. (Jupiter, Saturn)

Uranian planets: these are similar to Jovian planets but lack a metallic hydrogen layer. Masses range from 10 E to 50 E (0.03 J to 0.15 J); diameters from 30,000 km to 80,000 km. Atmospheres are mostly hydrogen but enriched in helium and methane. (Uranus, Neptune)

Terrestrial planets: this category (subdivided later) includes all planets which are largely rock and/or metal. (Mercury, Venus, Earth, Moon, Mars, Io, Europa)

Smaller rocky worlds (rocky planetoids?): this category could include rock/metal bodies smaller than planets (less than 2,000 km in diameter) but large enough to show some planetary characteristics (more than 400 km in diameter). This would include the three largest "asteroids" in our Solar System, which are believed to be the only asteroids which are not fragments of larger bodies (Ceres, Pallas, and Vesta).

Asteroids: these are small rock/metal objects (including moons). If the object's size is less than about 300 km, self-gravitation may not produce a near-spherical shape (many objects).

Ice planets: this includes solid planets (or moons) with a large fraction of icy composition. (Ganymede, Callisto, Titan, Triton, Pluto).

Smaller icy worlds (icy planetoids?): this intermediate category, like that above, includes objects with significant icy content smaller than planets (less than 2,000 km in diameter) down to about 300 km in diameter. This includes moons in our Solar System (7 of Saturn, 5 of Uranus) as well as a growing number of outer solar system objects orbiting the Sun and referred to as trans-neptunian objects (several dozen known). At the lower size limit this grades into...

Comets: these are smaller icy bodies--comets, smaller trans-neptunian objects, and small icy moons. Again, below 300 km they may not be spherical (many objects).

Some comments on these nine broad categories: three with significant gaseous envelopes, three rock/metal objects, and three ice/rock objects. The divisions between brown dwarf, Jovian, and Uranian are easy, since the different sizes cause phase changes in the interiors and produce significantly different objects. The distinction between rocky and icy categories is based on how much ice (or water); for example, Europa is on the edge here. However, the divisions given for the three size ranges for rocky/icy bodies are admittedly arbitrary. These categories are not proposed as profound delineations. Instead they are offered as a means of grasping some of the continuum of objects that are to be found. Given the variety of moons, asteroids, and icy objects in our own Solar System, you may begin to see the issue.

In any case, one of these categories is of primary interest to us: terrestrial planets. Note that this still encompasses a diverse range: a comfortable planet like Earth, uninhabitable Mars, the barren Moon (Luna, Earth's Moon), and the hostile environment of Venus. In subdividing this category, we run head on to our lack of data. The preceding categories were dictated by physics and the fact that same elements and compounds recur throughout the universe in similar proportions. Different types of terrestrial planets result from much more subtle combinations of a wider variety of factors.

IV. D. Planet placement

Using the previously discussed assumption, we find most planets in Star Trek designated by the system name and a Roman numeral indicating its sequence from the primary star (Earth would be Sun III). Table 4 lists the fraction of mentioned planets versus sequence from the primary star.

Table 4: Mentioned planets versus sequence in system

Sequence in systemnumberpercent of total
1 7 1.6
2 75 17.3
3 95 21.9
4126 29.1
5 55 12.7
6 20 4.6
7 30 6.9
8 6 1.4
9 11 2.5
10 2 0.5
11 0 0.0
12 5 1.2
13 0 0.0
14 1 0.2

Planets are tallied in table 4 if refered to in Star Trek. Most (but not all) are habitable planets, probably comparable to Earth. This implies that the most likely position for a habitable planet is fourth from the primary star, rather than third as in our solar system. Interestingly enough, this accident of Star Trek writing may make sense astronomically. The newly discovered planets orbiting other stars are often much closer to the primary star than Mercury. Thus, more planets within the habitable zone of a star makes sense. Fully half the planets are third or fourth in their system, and 80% from second to fifth.

Appendix A: Astronomy Background Information


The Earth is one of nine planets orbiting the Sun. The Solar System (these planets, moons, asteroids, comets, and so on) is quite small compared to the distance from it to the next nearest star, Proxima Centauri. In fact, if the orbits of the Solar System's planets were represented by a quarter, Proxima Centauri's distance would be the length of a football field. The Sun is one of about 400,000,000,000 stars in the Milky Way Galaxy. Many of these stars are multiple, unlike our Sun which is a single star. Only in the last few years have astronomers begun to discover planets orbiting stars other than the Sun.

© 2001 by Wm. Robert Johnston.
Last modified 10 September 2001.
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