# How would one go about making a star map for a planet that is within 50 ly of Earth?

I have a planetary system orbiting the star 18 Scorpii, 45.3 ly from Earth, and I would like to create a stellar map for it. My search for software showing the constellations from other stars has come up dry. Could any of you please help?

• If you have a list of distances along with a star map, you could write code to do it yourself. Convert the earth's star map to 3D by first inverting the projection and then scaling using the distance. Translate the coordinates by 45.3 ly in the appropriate direction. Project the transformed coordinates to a unit sphere (and apply the desired projection) to get the new star map. If you want brightness too, that would become a bit messy. – typesanitizer Jul 12 '17 at 17:11
• Possible duplicate of Creating a realistic world(s) map - Stars – Aify Jul 12 '17 at 18:16
• He just pointed out how it's not a duplicate. It's certainly related, so thanks for the link. Both points are worth seeing, no need to be grumpy. – The Nate Jul 12 '17 at 22:36
• Until I read this question (and answers) more closely, I interpreted it differently. As an interesting aside however, you may already know that there is a pretty cool website (created by Bruce Mills) that, among other things, shows what the stars in the sky would look like if looking back at Earth from several local star systems. Somehow he was able to come up with a program to generate this. This is the site: bdm.id.au/localspace – Jack R. Woods Jul 13 '17 at 16:44

I recommend Celestia (https://celestiaproject.net/). This is a very detailed (and free) astronomy simulator that lets you view planets, stars, constellations, etc. from any angle. You can view stars from other stars, even outside the galaxy. It's available for Windows, Linux and Mac OS.

Looking at 18 Scorpii from the direction of Earth (1.75 AU away):

Looking towards Earth from 18 Scorpii:

• I've used Celestia before. It's not terribly difficult to add in your own planets and objects, too. You just have to know a bit of astrophysics to input anything really valid. – Andon Jul 13 '17 at 21:12

I use software called Starry Night Pro. It allows you to "fly" to a star in the database and take a picture (with or without labels and guidelines). The software is not free, but it has many graphic options (from what I can tell on the comparison page, the cheapest version will accomplish this, the more expensive versions are for telescope control).

This is one of the export options of the starfield from 18 Scorpii (approximately 180° field of view – about half of the sky) with labels for bright objects and galactic guides:

You can also export semi-realistic images to use as backgrounds (here's another view from 18 Scorpii. Stars are slightly exaggerated in size to make them easier to see):

• Nifty package. I like. – The Nate Jul 12 '17 at 22:37
• How many ly away until you generally can't recognize our constellations? – Mazura Jul 13 '17 at 1:31
• At this point (47ly?) the constellations were already mangled. – wetcircuit Jul 13 '17 at 3:00
• If you look at my answer about Celestia, in the image as seen from 18 Scorpii, you can still see Orion in the bottom left, but a bit distorted. You can tell which stars are much closer than others. – Corwin62 Jul 13 '17 at 3:14

I spent some time putting together a project which does this to within 75lys, hosted here. All the source code is on GitHub.

This definitely isn't as professional as Starry Night, as mentioned above, but it is free. To be honest, I'm not at all an astronomer so I don't know to what degree 75lys captures all interesting constellations, so take the accuracy with a grain of salt.

• Welcome to Worldbuilding! Adding the second link should be fine now that you have some reputation. Posting multiple links as a completely new user is restricted in an attempt to reduce the amount of spam; it's annoying when legitimate users are caught in the crossfire, but at least in this case you quickly earned enough reputation to boost you past most new user limitations. – user Jul 12 '17 at 22:32
• Yeah makes sense. I've updated the post : ) – bpodgursky Jul 13 '17 at 0:11
• This is amazing! – Fattie Jul 13 '17 at 10:45

Maybe a little esoteric, maybe not, here is a stellar map to our sun that accompanied the Voyager space probe on its journey to the edge of our solar system and beyond. This placard was attached to the outside of the probe to explain its origins in case extraterrestrial intelligence ever found it.

Rather than using constellations which are only apparent from our particular vantage point in the galaxy it uses pulsars to pin-point the star of interest.

The lines all radiate out from our sun, or point in towards it depending on your point-of-view. The symbol with the two circles denotes a hydrogen molecule (H₂) which has a specific transition period. The assumption is that any sufficiently advanced civilization ought to be able to deduce this and it would be independent of any arbitrary time system.

Each of the lines projecting inward originates from a pulsar and the markings alongside it are a binary representation corresponding to the period of that pulsar measured in Hydrogen transition units. Instead of 0/1 the map uses -/|. The long unannotated line that extends downward was meant to point to a simplified drawing of the probe it was attached to in order to signify that this is where the probe originated from.

More detailed info about the selection of the pulsars can be found here.

CAUTION: This data is sufficient to start an epic galactic sim. You have been warned.

With great effort, I once assembled a starmap.zip including all the constellations and their exo-planets (as of 2004). Includes stars within 50 parsecs of Sol, and is a geocentric coordinate system.

The video link above is of the as yet uncompleted sim and uses the exact data files in the zip. Galaxy building is never done.

The astronomical data comes from the HYG catalog and uses the Bayer-Flamsteed (Brightstar) naming convention. 3D coordinates were calculated from luminosity values, along with the stellar classification for each star and its sol-scale radius.

I even made up some gamified names (related to their discovery date) for the planets, and gave them a few moons. There are over 3000 stars and over 30 exo-planets, which makes a nice looking sky.

For example, your star 18 Scorpius is listed as 18 Sco in the stars.hyg.csv file:

 18    Sco      16.26031482 -8.36823651 14.02524544 G1V             0.652


 18    Sco   A   (name) 1   1   (earth-scale radius)    (orbit AU)   true


Also included in the zip is line data for constellations (connect the dots). I included some icons for the constellations as well, which are nice.

Here is the line data for Scorpius from starlines.hyg.csv

  9Ome1Sco   14Nu  Sco
14Nu  Sco     Xi  Sco
Xi  Sco    9Ome1Sco
9Ome1Sco    7Del Sco
7Del Sco    6Pi  Sco
6Pi  Sco    5Rho Sco
7Del Sco   20Sig Sco
20Sig Sco   21Alp Sco
21Alp Sco   23Tau Sco
23Tau Sco   26Eps Sco
26Eps Sco     Mu 1Sco


and here is the icon for Scorpius:

Should look something like this when rendered (from Earth):

Note that 18-Sco is skipped in the actual line data, but is given for context.

The data is all tested and works perfectly (beautifully, really). The file formats are pretty obvious. There is no other documentation, so you will have to do some exploring to integrate it to your project. You will have to delete Pluto (2004, remember?)

I really do not want to revisit my epic galactic sim to reverse engineer the formats, hence the warning. That thing is a rip in my spacetime continuum.