A Sample Page from "Touch the Universe"
The Ring Nebula
The true colors in this image indicate different layers of gases: helium (blue), oxygen (green), and nitrogen (red). The outline of the outer layer of cool nitrogen is represented by a dotted texture; the middle hot layer with oxygen has a texture of parallel lines, and the very hot center area of helium, with a star, has no texture.
The Hubble Heritage Team (STScI/AURA)