So, I’m just going for aesthetics here. This new image of NGC 602 from Hubble looks great, doesn’t it? I enjoy how it achieves a wonderful (taken as literally as possible) sense of depth—in the nebula and beyond!
First off, the warm tones of the narrow-band emission trace out the presence of ionized gas, gas that’s been heated by the intense light from the cluster of stars near the center of the image. The continuum emission appears in cool colors, which yields a sense of depth. Cool, bluish colors appear to recede compared to warm, reddish colors—a natural repsonse to the everyday world, since atmospheric scattering makes more distant objects appear bluish (imagine the background of a Leonardo painting). This is somewhat deceptive since some of the ionized material may easily be more distant than the continuum, but overall, it gives a good impression of the dimensionality of the nebula.
But take a closer look! In the middle left of the image, you can easily spot a nearly face-on spiral galaxy (I didn’t take the time to figure out which one). And many other galaxies are scattered across the image, if you feel inclined to scrutinize a higher-resolution image or look at the Zoomify version.
NGC 602 is about 200,000 light years away, in the Small Magellanic Cloud, but the tiny galaxies are probably tens of millions of light years more distant. Talk about depth!