Expert: Ed - 7/6/2010

Question
The naked eye can see stars in space, are they, all part of our galaxy? And if it's part of our galaxy, are they showing a red shift? And if they are, that would mean that stars in our galaxy are all moving away from each other, so how can our galaxy still retain its shape? Wouldn't it, at a certain point, lose its shape, thus all other galaxy should be doing the same.

But we all know that other galaxy have a certain shape, and stars in our galaxy are moving away from the Milky Way, so that must be predicated for all other galaxies. Thus how can any galaxy retain its shape?

Answer
Kiet, the stars we can see with the naked eye are in our own galaxy, yes.  But they don't show a significant red shift, because the ones that are moving away from us are not doing so at the enormous speeds that produce the red shift effect.  Also, due to the swirling motion of our own galaxy, many stars are moving (roughly) TOWARD us, so if the have any "shift" going on in their light, it's actually a blue shift.  Google "blue shift" and see what comes up.
http://en.wikipedia.org/wiki/Blue_shift
http://en.wikipedia.org/wiki/Redshift

Redshift only becomes a factor with VERY distant galaxies, more than a few million light years away, moving away from us as the universe itself expands.  The nearby Andromeda Galaxy happens to have a small blue shift, because it is travelling in our own local group of galaxies, and happens to be drifting toward us.  The most distant galaxies always show red shift, which is one of the most important proofs of the Big Bang.

Our galaxy manages to keep its shape, due to the mutual gravitational attraction of the sum of its stars, compounded with the enormous gravity of the huge black hole in the center of our galaxy.

Keep Looking Up,
-Ed