Hand held Plexiglass model of spiral galaxy.
What it shows:
Handy size model of a generic spiral galaxy to show salient features or to describe structure of the Milky Way
How it works:
The model is a 30cm diameter Plexiglass disc 1cm in thickness, with a Ping-pong ball stuck through the center to represent the nucleus. The spiral arms of the galaxy are sprayed on with white paint, and we've stuck on a "you are here" arrow pointing to the outer reaches of one of the spiral arms at the approximate position of the Sun in the Milky Way.
figure 1. features of spiral galaxy model
The Milky Way has a diameter of about 30kpc, 1 making the scale 1cm = 1kpc. This makes the thickness of the Plexi almost correct for the thickness of the stellar disc (800pc).
T. Ferris Galaxies (Sierra Books, 1980) especially p.15
1 pc = parsec or 3.26 light years. 1kpc = 1000pc