Stellar Geography in the Babylon 5 Galaxy

A Map of our Galaxy

The following map of our galaxy (the "Milky Way") is taken from the 1994 Cambridge Atlas of Astronomy. I have rotated it so that Earth's sun ("Sol") appears at the bottom left, since that is the same perspective used in the Babylon 5 "War Room Map".

Where is Earth?

Earth orbits "Sol", a star which we commonly refer to as "the Sun". Our nearest neighboring stars are just over 4 light-years away. Farther out, astronomers have counted 59 stars within 17 LY of our sun.

There are over 100 000 000 000 stars in the Milky Way Galaxy. The Core of the galaxy is an ellipsoid with 5000 LY as its vertical radius and 10000 LY as its horizontal radius. The entire galactic disk has a horizontal radius of 50000 LY; our sun is around 30000 LY from the center.

Thus, leaving Sol and heading through Sagittarius, it is 20000 LY to the edge of the Core and another 10000 to the galactic center; heading through Gemini it is around 20000 to the horizontal edge of the galaxy. But one can leave the galactic disk by heading "vertically" a mere 1500 LY.

Note from the map that our sun isn't actually in the local (Sagittarius) arm. But the spaces between the arms still contain stars. The motion of stars in a galaxy is very odd – the stars rotate about the center of the galaxy at a much different rate than the spiral arms rotate! Think of the stars as cars, and the arms as "traffic jams" on a freeway – the speed at which the "jam" moves doesn't match the speed of any car. See the texts mentioned at the end for more information.

Thus, there is no "edge" or "rim" to the galaxy. (David Gerrold once commented that trying to find the "edge" of the galaxy is like trying to bisect a sneeze.) We will merely see a gradual increase in the distance between stars as we "leave" the galaxy.

Over 90% of stars can be categorized by their spectra into the classes O B A F G K M . These run from hotter to colder; loosely, we may think of O-type stars as green-white, B as blue-white, A as white, F as yellow-white, G as yellow, K as orange, and M as red.

Other classes exist as well (such as D, white dwarf stars). Our sun is considered a G2 V star: a small yellow star.

Where are Earth's Colonies?

Earth itself has a couple dozen colonies, many of which have been referred to by their colonial names. But the only worlds given real astronomical names are:

• Proxima, or Alpha Centauri C ("Proxima Centauri"), 4.226 LY from Earth. This has been mentioned many times in every season of Babylon 5. (Astronomers are currently debating if Proxima Centauri should really be named "Alpha Centauri C", but its location is clear.)

• Vega, or Alpha Lyrae, is 25.167 LY from Earth. It, too, has been mentioned several times.

• Arcturus, or Alpha Bootis, is 35.8 LY from Earth. It has only been mentioned once (in The Parliament of Dreams, season one).

• Antares, or Alpha Scorpii, is much further – 520 LY from Earth. It was mentioned only once, in The Gathering, the pilot episode. But "Antarean Flarn" was mentioned in The Parliament of Dreams, in season one.

• Deneb, or Alpha Cygnus, is 1600 LY from Earth. In Parliament of Dreams, Catherine Sakai mentions visiting "the Deneb Sector", but the meaning of "sectors" in the show is unknown and inconsistent. But in season four, Earth's colony at Deneb IV was discussed in Racing Mars.

There have also been several "Orion" colonies mentioned, but there are a whole lot of stars in the constellation Orion, including the nearby Pi-3 Orionis (26.09 LY from Earth), which Richard Wakefield has suggested may be the home of the Orion Colonies.

Where is Babylon 5?

This question has seen a variety of interesting answers. It seems likely that Straczynski hasn't been keeping careful track of some of the astronomical data in his show.

In the earliest days of Babylon 5, Straczynski was asked about the location of the space station. Between 1993 and 1994, he variously claimed that Babylon 5 was "in a star-system about 35 light-years from Earth"; that Babylon 5 was "in an undiscovered star-system about 25 light-years from Earth"; or that Babylon 5 orbited a star named Tigris.

One early JMS post even included the bizarrely impossible claim that Babylon 5 is in a star system "that hasn't been discovered at this point in time . . . but in about 50 years, it'll show up on the starcharts. It's a fairly small star, dwarfed and hidden by several nearby binaries that overwhelm the spectrum visible from Earth."

The televised show said nothing of this. We saw Babylon 5 in orbit about an orange planet, which itself orbited a yellow star. The star's name was not given, but the planet was called Epsilon 3.

Finally, Stracyznski seemed to settle on a choice for B5's home star:

We have seen in several shows – most notably in Interludes and Examinations – that Babylon 5 and Epsilon 3 orbit a star which is yellow-white in appearance. Indeed, the star looks a whole lot like our sun.

Epsilon Eridani is a K2 star, basically orange to orange-red in color. Like our sun, if one looked directly at it, the star would appear white, but it would have an orangish corona. The star we've seen in the show is white with a yellow-white corona.

Bob Donahue points out that Epsilon Eridani is only about one billion years old, and thus probably too young for interesting life to have evolved. So far, this isn't a problem – there's no reason to believe that any of the races we've seen in the Great Machine on Epsilon 3 are native to the planet.

Epsilon Eridani is 10.67 light-years from the earth (according to the 1991 Gliese list; see appendix for sources). This is certainly much closer than the 25 or 35 light-years mentioned earlier. It also contradicts some more recent data: in Face of the Enemy, Lise Hampton Edgars tells Garibaldi that she didn't want a relationship with someone who was "18 light-years away". Of course, she may simply have forgotten B5's true distance in her annoyance with Garibaldi.

So we seem to have a few possible options:

• We can accept that Babylon 5 is in the Epsilon Eridani system. It seems odd that the newscaster would refer to this as the Epsilon Eridani "sector", and we have to assume that the star's color is not shown correctly. Nearly all stars in the show are shown as "yellow"; this may simply be artistic license (like sound in space, or the fact that space in Babylon 5 seems more often blue or purple than it is black.

• Perhaps B5 is in the "Epsilon Eridani Sector", a huge region of space. This seems odd, since Epsilon Eridani is fairly insignificant as stars go; it seems odd to name a "sector" after it.

• Perhaps sectors are small. Then B5 is very close to Epsilon Eridani. There are only two star-systems under six light-years from E Eridani:
  • One is Tau Ceti, 5.3 light-years from Epsilon Eridani, and 11.40 LY from Earth. It is G8 (yellow or orange-yellow). This would be a good candidate. But Tau Ceti is as bright, as close, and as well-known as E Eridani. Why not refer to it by name, instead of assigning it to E Eridani's "sector"?

  • The other is UV Ceti, 5.2 LY from Epsilon Eridani, and 8.57 LY from Earth. The UV Ceti system contains a pair of M5 red dwarfs. But there are at least two problems here: UV Ceti is only 2.9 LY from Tau Ceti – so shouldn't it be in the "Tau Ceti sector"? The other is that red dwarfs are small, cold, and don't look like the star we see on TV.

  • There could be an undiscovered star a few light-years past Epsilon Eridani. Seriously! Some of those red stars are tiny. But we're talking about a real M9 here, and orbiting this thing wouldn't feel much warmer than orbiting Jupiter.

• I've included an appendix with lots of interesting and relevant stars, so you can invent your own hypotheses. I have a feeling that JMS is gonna stick with Epsilon Eridani, so we will just have to ignore the numbers he quotes for distance, and hope that Ted Turner colorizes the star in some future Special Edition.

Where are the alien homeworlds?

Fragments of information regarding the other alien worlds were given during the first season of Babylon 5:

• In The War Prayer, when Londo is talking to the young Centauri runaways, he says that Centauri Prime is 75 light-years from Babylon 5.

• Londo also mentions that his people, the Centauri, refer to Earth as Beta 12.

• We know that the Centauri Republic does not contain the Alpha Centauri system. Long ago, JMS claimed that the Centauri do not come from any star in the constellation Centaurus, but rather that's where humans "met" them. This certainly seems odd, as humans had no faster-than-light travel at the time, so even if a human slowship met them in a Centaurus constellation, the mass of humanity would have met them when they visited our system afterwards!

• In By Any Means Necessary, Sinclair and G'kar discuss the location of Narn. We learn that Narn is about 12.2 (Earth) light-years from Babylon 5, and that it's exactly 10 Narn light-years plus 24 Earth light-hours from B5. This is one figure JMS hasn't forgotten; he later posted, "In one episode, we mention that B5 is 12 of *our* light years from the Narn homeworld, which is equal to about 10 of their years."

• The Markabs, featured in Confessions and Lamentations, share their name with a real star (Alpha Pegasi is named "Markab"), but when Straczynski was told of this he said he was unaware of it, and that the Markab's don't hail from that system.

• Richard Wakefield asked JMS about the correspondence between real space and hyperspace. On 29 June 1996, Straczynski replied:

  No, what I said was that *time* works about the same way in hyperspace, not distance, nor that there was necessarily a proportional 1-1 corrolation between realspace and hyperspace. There's still some distance involved in hyperspace, yes, though again there isn't always a 1-1 corrolation. It takes 3 days to get to Earth. It takes 4 days to get to Centauri Prime, even though CP is almost twice the distance from B5. It's *extremely* confusing to navigate hyperspace, which is why you need the beacons and transfer points, or it's extremely easy to get permanently lost.
  -- jms

Possibility One. Babylon 5 is in the Epsilon Eridani system. JMS was correct when he said that Centauri Prime is "almost twice" as far from Babylon 5 as is Earth. In this case, Babylon 5 is 10.67 LY from Earth, 10 LY from Narn, and around 20 LY LY from Centauri Prime. (We must conclude that the Centauri year is very short and Londo was referring to 75 Centauri light-years.)

One possible problem with this is that Narn, the Earth Alliance, and the Centauri Republic have each founded several colonies. Putting all three this close seems to make things very complicated.

• If we further assume that Centauri Prime is in the constellation of Centaurus, we have a very limited choice of systems (Centaurus and Eridanus are not in the same direction at all!) A star which is in Centaurus and under 22 LY from Epsilon Eridani must be under 18.7 LY from Earth.
  • Perhaps Centauri Prime orbits a red dwarf (which would explain the short year!) There are several possible candidates in this case.

  • There are only two candidates which aren't red dwarfs. One is the Alpha Centauri system itself (12.9 LY from E Eridani), but JMS specifically said Centauri Prime is not Alpha Centauri. The other is Luyten 145-141, a white dwarf star right on the border of the Centaurus constellation (it's in Musca, actually) which is 14.93 LY from Earth and 19.9 LY from Babylon 5.

• Choosing a location for Narn is a bit tricky now: we'd like Narn to be not too close to Earth, so we can put it on the "far side" of B5. Yet this makes it seem that the Centauri should have found Sol before finding Narn!

• Specifically, we have a fairly rectangular postage stamp of space, with corners at 11:05 RA -36 Dec 72 LY, 11:20 RA -64 Dec 74 LY, 14:40 RA -64 Dec 71 LY, and 15:00 RA -30 Dec 67 LY. The final such corner is the least likely, since it puts Earth almost directly between Centauri Prime and Narn. Bret Feinblatt suggests Iota Centauri, a white A2 star about 66 LY from Earth, as a good candidate.

• If we wish Earth to be reasonably far from Narn and from the Centauri-Narn route, we might have Centauri Prime around 11:30 RA -62 Dec (about 73 LY from Earth and 75 LY from E Eridani), and have Narn somewhere in the southern hemisphere near 5:00 RA. The best choice for Narn might then be 82 Eridani (also called e Eridani). This is a yellow star 13 LY from the Babylon 5 station, 20 LY from Earth, and 67 LY from Centauri Prime.)

Finally, we should note that nothing has been said about the location of Minbar, Vorlon, Z'ha'dum, or the other alien worlds.

How far does "known space" extend?
What is the "Rim"?

According to all the evidence above, the Centauri homeworld, the Narn homeworld, and the Babylon 5 station are less than 100 light-years from Earth. Moreover, all Earth colonies mentioned in through season three were within 38 LY of Earth – except for Antares, mentioned in the pilot.

Many viewers (including myself, the author of "Babylon 5 A to Z", and the authors of the "Babylon Project Role-Playing Game") concluded that this reflected the intended scope of the show.... in other words, all the action in Babylon 5 takes place within 100 or 200 LY of here.

If you study the map above, this would mean that the entire show takes place in the "dot" marking Earth's sun on the map!

The first questions arose as characters began to refer to "the Rim". There seemed to be two main possibilities for what this could mean: the "rim of known space", or "the rim of the galaxy".

The rim of the galaxy is quite far. Going towards galactic "north", one can "exit" the galactic disk after a journey of around 1500 light-years, but one is hardly "outside the galaxy" at that point. The stars are just much further apart.

The term "rim" was usually used without any modifiers. In the first two seasons, there were only two exceptions to this rule:

• In A Distant Star, Captain Jack Maynard is not too thrilled with his job of mapping new regions of space. He complains, "Oh, back out to the rim. The NEW rim, now that we've finished mapping Sector 900. We're hoping to build two new jumpgates by the end of the year, and then have Earth follow up with survey ships." This clearly suggests that the "rim" is the edge of known space, and thus it recedes as humans and other races explore our region of the galaxy.

• In The Geometry of Shadows, Elric is taking his band of technomages far from all known worlds. He says they will not stop until they reach the galactic rim.

However, Seasons Three and Four completely changed this view.

In Matters of Honor, the season three opener, Morden shows Londo a map of the galaxy, and offers to divide it up between the Centauri and the Shadows. This map was shown three times and each time it was a slightly different map! Presumably the special-effects people are at fault. Here is one version of this map:

And in the new "War Room", the wall map shows the entire galaxy, with notes all over the galactic disk.

These maps seemed to imply that the show takes place on a fully galactic scale – despite the fact that Season One and Two indicated that the Narn and Centauri capitals, and Babylon 5 itself, are less than 100 light-years from Earth.

Also, in Voices of Authority, Delenn is re-telling the story of the Old Ones – but this time instead of saying that they "passed beyond the Rim", she explicitly says they "passed beyond the Galactic Rim".

At the same time, JMS began stating that the "rim" is definitely the rim of the galaxy. In a message to Richard Wakefield (20 August 1996), he wrote,

"It's the Rim of the galaxy, and once you come out of hyperspace past the galactic rim, all your points of reference are gone, and getting back is tough, if not impossible . . . and you can't just "keep going" in a straight line in hyperspace, as it's not a one-to-one corrolation to normal space."

Indications of the large scale continued to appear. Deneb was mentioned as a human colony; as mentioned above, this is 1600 LY from Earth. This also made it reasonable to suppose that the mention of Antares (520 LY) in the pilot had not been an error.

But the most important factor was the Shadow War. It is quite clear from all the dialogue between Lorien, the Shadows, the Vorlons, and the other "First Ones" that Lorien wanted them to leave the galaxy, and much of their discussions seem to imply that the First Ones have been shepherding "all the young races in the galaxy", not just in one tiny neighborhood.

For example, in Into the Fire, all the older races are speaking as if the Vorlon-Shadow sphere of influence is the whole galaxy, and the First Ones who became bored of this place went "beyond the rim, to the emptiness which lies between the galaxies". Aside from the oddness of the belief that one would find qualitatively different things outside of our galaxy, this again suggests a large scale to what has been going on. In particular, how can Lorien and Ivanova be sure they have contacted all the First Ones in the galaxy, unless the White Star really did travel the entire width of the galaxy?

Compromise: The War Room Map.

Finally, some sort of "compromise scale" emerged. At the World Science Fiction Convention (Labor Day, 1996), Straczynski stated that the "Rim" does indeed refer to the "rim of the galaxy", but that the show's action does not fill up the entire galaxy. Rather, the scope of Babylon 5 is a "pie slice" of the galactic disk.

This was aptly illustrated in And The Rock Cried Out, No Hiding Place. Sheridan and Delenn are studying recent Shadow attacks, and they graphically plot these attacks on the War Room Map. What follows is the War Room Map graphic, with the region they plotted outlined in green:

Appendix:
Table of interesting stars

Stars listed in this table include: all stars within 11 light-years of Sol; all stars between 11 and 17 LY of Sol except Type M red dwarf stars; all stars with Bayer designation "Epsilon" within 50 LY of Sol; and stars with "Eridani" in their names within 50 LY of Sol.

(The last category is somewhat vague, since there are so many ways to name stars. Past 25 LY, I haven't included stars like "544 Eridani" which generally go by other names. There really isn't much reason to link Babylon 5 to the name "Eridani" in the absence of the letter "Epsilon" anyway.)

Also included: Vega and Deneb; Pi (3) Orionis, which Richard Wakefield has suggested as a possible location for the Orion Colonies; and the Orion Belt Stars (Delta, Epsilon, Zeta) which Chris Russo has suggested may be the origin of the term "Orion Belt Alliance".

I plan some updates to this section soon, plus some discussion of the stars given in the Babylon Project Role-Playing Game.

Right Ascension is in hours east of the standard meridian (close to Alpha Andromedae). Declension is in degrees north/south of the equator. Distance is in light-years from the earth.

Magnitudes under 10 are given. You can see up to 6 or so by eye, and up to 8 or 9 with binoculars. Over 9, you need a telescope, and if you've got one, you have a better star chart than this anyway.

Color gives the spectral class and a rough color translation.

The x , y , z coordinates are in light-years, with Sol at the origin. The z-axis points towards Earth north (Polaris, basically – 23 degrees from Solar north and XX degrees from Galactic north. The x-axis points towards 0 Hours Ascension (Andromeda, and the Capricorn/Pisces border) while the y-axis points towards 6 Hours Right Ascension (Betelgeuse, and the Taurus/Gemini border). These are simply the natural cartesian coordinates which correspond with the spherical (ascension/declination) coordinates.

The Ascension/Declination figures were rounded after the x,y,z were calculated. The x,y,z are considered most useful here, because they make it easy to calculate the distance between any two stars in the table.

Name	RtAsc	Decl	Distance	Mag	Color	x	y	z
Sol	--	--	0	-27	G2 yellow	0	0	0
Proxima Centauri	14:26	-62.5	4.226	11	M5 red dwarf	-1.57	-1.16	-3.74
Alpha Centauri	14:36	-60.6	4.355	-.01 1.3	G2 yellow K0 orange	-1.66	-1.35	-3.80
Barnard's Star	17:55	+4.5	5.981	9.6	M5 red dwarf	-0.2	-5.9	+0.4
Wolf 359	10:54	+7.3	7.797		M6 red dwarf	-7.4	+2.2	+1.0
BD +36 2147	11:01	+36.3	8.209	7.5	M2 red dwarf	-6.4	+1.7	+4.9
Sirius	6:43	-16.6	8.574	-1.4 8.4	A1 white DA white dwarf	-1.6	+8.1	-2.5
UV Ceti (L 726-8)	01:36	-18.2	8.567		M5 red dwarf M5 red dwarf	+7.6	+3.4	-2.8
Ross 154	18:47	-23.9	9.56		M4 red dwarf	+1.8	+8.6	-3.9
Ross 248	23:39	+43.9	10.33		M6 red dwarf	+7.3	-0.7	+7.1
Epsilon Eridani	3:31	-9.6	10.67	3.7	K2 orange	+6.46	+8.46	-1.81
Ross 128	11:45	+1.1	10.83		M4 red dwarf	-10.9	+0.7	+0.2
Luyten 789-6	22:36	-15.6	11.08		M5 red dwarf M5 red dwarf	+9.5	-3.7	-2.9
Epsilon Indi	22:00	-57.0	11.29	4.7	K5 orange	+5.2	-3.1	-9.4
61 Cygni	21:05	+38.5	11.30	5.21 6.03	K5 orange K7 orange	+6.2	-6.0	+6.8
Tau Ceti	01:42	-16.2	11.40	3.5	G8 yellow	+10.1	+4.8	-3.3
Procyon	7:37	+5.4	11.41	0.4 11	F5 yellow-white DA white dwarf	-4.7	+10.3	+1.0
Kapteyn's Star	5:10	-45.0	12.63	8.9	M0 orange-red	+1.9	+8.7	8.9
van Maanen's Star	0:47	+5.2	14.13		DZ7 white dwarf	13.3	+2.7	+1.2
Luyten 145-141	11:43	-64.6	14.93		DQ6 white dwarf	-6.8	+0.5	-14.3
BD 50 1725	10:08	+49.7	15.30	6.6	K2 orange
Omicron (2) Eridani 40 Eridani DY Eridani	4:13	-7.7	15.75	4.4 9.5 11	K1 orange DA white dwarf M4 red dwarf	+7.0	+14.0	-2.2
Altair	19:48	+8.7	16.23	0.8	A7 white	+7.4	-14.5	+2.4
70 Ophiuchus	18:03	+2.5	16.39	4.2 6.0	K0 yellow-orange K5 orange	+0.2	-16.7	+0.7
82 (e) Eridani	3:18	-43.3	20.44	4.3	G5 yellow	+9.5	+11.2	-13.9
Rho Eridani	1:38	-56.4	21.90	5.8 5.9	K2 orange K3 orange	+10.7	+4.8	-17.8
Pi (3) Orionis	4:44	+6.8	26.09	3.2	F6 yellow-white
Vega	18:34	+38.7	26.52	.03	A0 white
Delta Eridani	3:41	-9.9	31.51	3.5	K0 yellow-orange	+16.5	+23.7	-5.1
CC Eridani	2:32	-44.0	37.4	8.9	K7 orange
58 Eridani	4:45	-17.0	41.3	5.5	G1 yellow	+12.9	+38.3	-12.4
Tau (1) Eridani	2:43	-18.8	44.7	4.5	F6 yellow-white	+3.9	+29.1	-15.3
Epsilon Ceti	2:37	-12.1	47.5	5.5 5.6	F8 yellow-white M0 orange-red	+35.7	+29.2	-9.9
Epsilon Reticuli	4:16	-59.4	48.7	4.4	K2 orange
Epsilon Phoenicis	0:07	-46.0	50.6	3.9	K0 orange subgiant
Tau (3) Eridani	3:00	-23.8	52.9	4.1	A4 white
Epsilon Cygni	20:44	+33.8	62.7	2.5 13.4	K0 orange subgiant M4 red dwarf
Epsilon Scorpii	16:48	-34.3	66	2.3	K2 orange subgiant
68 Eridani	5:06	-4.5	67	5.1	F2 yellow-white
Epsilon Ursa Major	12:53	+56.1	68	1.8	A0 white
Zeta Orionis	5:38	-02.0	136	2.1 4.2	09 white giant B0 white subgiant
Delta Orionis	5:29	-00.3	233	2.2 6.9	O9 white giant B2 white
Epsilon Orionis	5:34	-01.2	far	1.7	B0 white giant
Deneb	20:40	+45.1	1500	1.3	A2 white giant

Appendix:
Links to astronomical web-sites

First, some written references:

• Peter van de Kamp, "The Nearby Stars", Annual Review of Astronomy and Astrophysics, Vol. 9, 1971, pp. 103-126.

• W. Gliese, "Catalogue of Nearby Stars", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, No. 22, 1969.

• W. Gliese and H. Jahreiss, Third Catalogue of Nearby Stars, in preparation. See web-site below.

• Ian Ridpath, Norton's 2000.0, Longman, 1989.

• Cambridge Atlas of Astronomy, Cambridge University Press, 1994. This contains the map at the top of this page and many beautiful illustrations.

• James Binney and Scott Tremaine, Galactic Dynamics, Princeton University Press, 1987. If you would like a description of the motion of stars in our galaxy, this is your source! Some background in math and physics won't hurt (this is a standard first-year grad school text).

And some on-line references: