Celestia Forums

I am quite confused. I have loaded the preview of Celestia 1.50 and the galaxy arms look great; but to me they look the wrong way round.
A while ago I made, for my own amusement, a fictional map of the galaxy based on various artist's impressions; this was released as an add-on for the OA universe.
Here it is as seen from galactic north;


I based it on these images,


and
http://www.atlasoftheuniverse.com/milkyway.html
which I have always presumed were drawn as if seen from galactic north.

But the spiral arms included in the new version 1.50 seem to face the other way; as seen from galactic north again;


I know I have been mistaken about galactic coordinates before, but can anyone explain where I have gone wrong?

It does seem that the Milky Way model in Celestia v1.5 is reversed.

The standard plots of the Milky Way arm structure have galactic longitude increasing in a counter-clockwise direction. In other words, they represent the Milky Way as if seen from galactic North. They show the arm separation increasing with increasing longitude.

See, for example, the plot at
http://cfa-www.harvard.edu/~reid/background.html
which is taken from Georgelin and Georgelin (1976).

A more recent study (including color plots) is
http://arxiv.org/pdf/astro-ph/0605728
The Spiral Structure of the Outer Milky Way in Hydrogen (2006)
Authors: E.S. Levine, Leo Blitz, Carl Heiles

Oh; so I was right, after all.

I admire the new Milky Way model; and if it can be adjusted so that the arms face in the right direction I will be very happy.