Red Shift, Blue Shift, and the Stars on my Desktop

So here’s a pic of my desktop. It would appear that some of the stars appear red, and some blue. Is this due to the red shift/blue shift thing I once read about? Some are going away, some are moving closer? Also, the larger stars have “compass points” coming off them (for lack of a better term) Is this a result of the telescope lens? Or would this visible with the naked eye? (assuming I was actually floating around out there, which would be pretty cool. For awhile, anyway) Are these Hubble pics re-touched in anyway?

No. You can’t actually see the red or blue shift or a moving star (long explanation available on request). The colors of the stars you see are due to their temperature. Cooler stars tend towards red, while hotter stars appear bluish. The spikes you see are artifacts caused by the thin arms that hold the small secondary mirror in some types of reflector telescopes.

A couple of other points (well, okay, three):

  1. Hubble doesn’t have a lens, it has a mirror. Actually, several!

  2. The images are indeed “retouched”, but it’s not a simple airbrushing. It’s a long process to get images from the 'scope to your desktop. Check out this short page by a Hubble imaging specialist, and also take a look at this series of pages from the same guy describing the steps. Cool stuff.

  3. I’ll add that stars behind thick layers of cosmic dust also can look red. The dust absorbs blue light, leaving only the red. It’s an interstellar version of a red sunset here on Earth.

The “compass points” are artifacts caused by the telescope design. The Hubble telescope optics consist of a primary mirror and a secondary mirror, as well as numerous lenses and mirrors that direct the light to individual instruments. The secondary mirror is supported by four legs, and these are in front of the primary mirror directly in the light path. Since light is a wave it tends to bend around edges (diffraction). The curved edge of a circular mirror creates a circularly symmetric diffraction which merely degrade the sharpness of the image, but the straight edges of the secondary mirror support create the sharp spikes which you see - not only on the Hubble, but on most large astronomical telescopes. Similarly, photographic and movie cameras usually have hexagonal stops (adjustable apertures) and the straight edges of the hexagon create six-pointed star patterns. Here is an example I noticed in a photo I took recently.