# Overhead (galactic North) view of the stars in and around the Vela Constellation with distance

I am working on a project and would like to have a star map--seen from "above" (Galactic North?) that calls out the stars in the Vela constellation and shows their distance from sol / earth.

I realize that any 2D map will not show the Z-axis, but I'm okay with that (especially if there's a notation).

I want to be able to show which stars in the Vela constellation are closer to earth vs. further away.

Is there anything like this? I've looked and can't find it.

• There are a zillion stars within the boundary of any given constellation, so it will be easier to answer if you can mention which stars you are interested in. For example, in the Wikipedia article (I added the link to your post) it says that there are 5 stars brighter than magnitude +3. Are those sufficient?
– uhoh
Oct 14 '19 at 8:20
• astronomy.stackexchange.com/questions/13488 has a lot of astronomy data, and you might find what you want there. The HYG database mentioned there may be particularly useful. Since this is a specific project that may not be of general interest, feel free to contact me directly (contact information in profile) for free help.
– user21
Oct 14 '19 at 16:56

note: I'm about to practice Astronomy without a license, if I've said something wrong please feel free to comment or just edit and correct it, thanks!

Wikipedia's Vela (constellation) lists its brightest stars and links to each star's Wikipedia page. Here are the first five of them:

On each page at the bottom of the data box on the right side there is a link to the star's page in Symbad. For Gamma Velorum (HD 68243) for example, the page is http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+68243

On that page you can see the galactic coordinates (GAL coor) are about 262.806, -07.697 and since you only want a 2D map use the azimuth (262.806) to draw a line from our position in the solar system, which is the origin of galactic coordinates (for more on that see answers to How was the galactic plane established? and also can you translate a GPS coordinate to a Galactic coordinate.

Now how far away is the star from us on that line? Use the parallax value for that. For the Gamma Velorum example it is about 3.556 milliarcseconds. the distance to an object (measured in parsecs) is the reciprocal of the parallax (measured in arcseconds). So the distance here is 1/0.003556 or 281.2 parsecs which is about 917.2 light years.

For your 2D projection on to a flat map, you'll need to foreshorten that distance, so multiply by cos(altitude): $$\cos(-07.697)=0.9910$$ so you put your dot along the azimuth line at 917.2 times 0.9910 = 908.2 light years.

You'll have to decide what to do if one of the stars is far away from the plane of the galaxy, because the projected distance won't accurately reflect the actual distance.

If you can narrow this down to a number of stars that makes the project manageable, you can make your own 3D map. It's easy. First, find the X,Y,Z galactic coordinates. X is the distance of the star from the sun in the direction of the galactic center. Y is its distance from the sun in the galactic plane perpendicular to the X axis in direction of the sun's orbit. Z is the height (relative to the sun) above the galactic plane. The galactic plane is somewhat arbitrary, but can be taken as about 70 light years "south" of the sun.

Now build your model. I used a large square foam board, stiff wire and small spherical foam balls (from Michael's). You could upgrade this easily. Plot your X and Y axis on the foam board. The Z measurement would be the length you cut of the stiff wire. Z=0 does not have to be on the board since some stars will be "south" of the sun. Of course, you would want to have to have the same scale for each axis (ie. 1 inch = 10 light years).

You could determine the distance fairly accurately mathematically given the X,Y,Z coordinates. However, if accuracy is not important, just measure the distance from the sun to the star with a ruler and use the scale. (If Z=0 is not on the board you would have to use a foam ball for the sun, too.)

• I need to mention that I found X,Y,Z for my stars using www.stellar-database.com, but only stars within 75 LY are in this listing. To calculate X,Y,Z for your stars, first determine RA,DEC and distance(d) for a star (Wikipedia, J2000) then calculate galactic longitude (l) and galactic latitude (b) using this on-line tool robertmartinayers.org/tools/coordinates.html. (use the "modern" (b) and (l) result and be careful with signs). Then use the formulas: X=dcos(b)cos(l), Y=dcos(b)sin(l) and Z=dsin(b). These will be year 2000 positions. Oct 15 '19 at 5:47
• You will see that the brighter Vela constellation stars vary greatly in distance from the sun. Most of the stars we see in the sky are not the closest ones. Oct 15 '19 at 5:49