The Nostromo Files Investigates… An aid to interstellar navigation

I’ve been in love with the stars since before I can remember, and as the internet provided places where I could learn more about them, my interest grew to the point of joining a local astronomy club.

Seeing the excitement over Fria Ligan’s ALIEN RPG and its star map, I thought I would share some information with those who like digging a little deeper to bring verisimilitude to their gaming, their fiction writing, and other imaginative pursuits.

This article I found recently (“Tales of Known Space”, by SF writer Alastair Reynolds) delves into the topic of “galaxy-building”: that enjoyable mental exercise of creating interconnected, colonized worlds amongst which a futuristic society might seek life, liberty, and the pursuit of happiness (as they see it).

To help with such creative pursuits, there are places like the NASA Exoplanet Archive and that provide details and galactic coordinates of stars and planets.

Knowing your Right Ascension from your Declination, and the difference between the two, is important. Click here for an article on the topic, over at Sky & Telescope.

This deleted scene from Alien (“Alien Transmission”) is all the better for including RA and Dec in the dialogue, I think.

I imagine the base for the planetoid’s position is the Nostromo itself.

But how do you figure out the distance between two stars when one of them isn’t the Sun? That requires, as Reynolds writes in his article, some pretty fiddly and time-consuming math.

Or you could try searching the internet for ready-made calculators.

I have found one to share with you. Let’s experiment with it, using some familiar objects in the Alien universe, shall we? I think we will use The Sun, Zeta 2 Reticuli, and Epsilon Reticuli (the location of Thedus, according to Scott Middlebrook (The Alien Universe Timeline).

The coordinates for the celestial bodies came from If you visit the site, you will note that they use the following format for coordinates RA and Dec:


So, the location of Zeta 2 Reticuli, written in that format, is: 03:18:12.8-62:30:22.9

I simplified it to a format I am more familiar with: RA 03h 18m 12.8s Dec -62° 30′ 22.9

celestial bodyright ascension (ra)declination (dec)
Sol (The Sun)00h 00m 00s00° 00′ 00
Zeta 2 Reticuli03h 18m 12.8s-62° 30′ 22.9
Epsilon Reticuli04h 16m 29.02s-59° 18′ 7.8

The site we’ll look at is WolframAlpha’s “Distance Between Two Star” Widget. I used it to create a “road atlas” distance comparison chart, much like we used to use back in the old days before online maps made cross-country driving much simpler. Select a celestial body from the left-hand column and follow that row to the right to see the distances from that body. For example, The Sun is 59.49 ly from Epsilon Reticuli.

SolZeta 2 ReticuliEpsilon Reticuli
Sol 039.38 ly59.49 ly
Zeta 2 Reticuli39.38 ly021.15 ly
Epsilon Reticuli59.49 ly21.15 ly0

Nostromo travels 0.13 light years per sidereal day when fully laden. Given these distances, the calculator came up with this:

It takes Nostromo a little over 15 months (458 days) to travel from Thedus (Epsilon Reticuli) to Earth (Sol).

It took Nostromo approximately 5 months (162 days) to travel from Thedus to Zeta 2 Reticuli.

The Nostromo‘s journey home from Zeta 2 Reticuli was approximately 10 months, matching Lambert’s estimate.

I don’t know about you, but these little exercises are fun! Fortunately, timeframes in Alien were relatively vague, so it’s cool that using these calculators doesn’t directly contradict anything we see or hear in the film.

I hope this calculator is useful to those writing game scenarios, sci-fi stories, or who just want to play around with the numbers.




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