Expert: Ed - 4/20/2008

Question
I was wondering how we see the constellations.i know they are in the milky way but why and why do we see the milky way in some constellations and some not

Answer
Hady,

It is affected by how you use the term "Milky Way."  The term can refer both to A.)the galaxy that our sun is part of, along with billions of other stars, or B.)the light colored stripe across the sky, which we can see on a clear night.

The light colored stripe is our galaxy, seen edge-on.  For example, when you look at the constellation Sagittarius, you are basically looking toward the center of our galaxy.  On each side of that constellation, you can see the Milky Way stretching out.  It is the view of our galaxy in which the density of stars is the highest, so it looks sort of light-colored.

But there are lots of constellations in which the Milky Way is not visible.  Those constellations are still composed almost entirely of stars in our galaxy, which we also call the Milky Way.  So, those constellations are part of the Milky Way galaxy, even though the stripe of light that we call the Milky Way doesn't necessarily run through them.

This is not a huge plot to get you confused, even though it seems like it might be.  It's just a confusing topic.

I hope this makes sense.  Please get back to me if you are still lost, and I will try again.

Keep Looking Up!
--Ed