Expert: Ed - 1/15/2008

Question
Where are the constellations located in terms of out solar system?  Are Leo, Sagittarius, Virgo etc. in the Milky Way galaxy or are we seeing stars from other galaxy's?  and on that note, can we see stars in other galaxy's, like Andromeda, or is ever star in the sky from the milky way?

Answer
Jeph,
The constellations do not really exist, of course, they just appear to be patterns in the stars, as seen from Earth.

Anyway, the stars in them are all located far outside of our solar system.  For perspective, you should realize that the sun's light takes just a few minutes to reach the planets Mercury, Venus, Earth and Mars.  It takes about 43 minutes to reach Jupiter, and, approximately, a few hours to reach the more distant planets in our solar system.

OK, so light, travelling at 186,282 miles per second, takes, at the most, several hours to reach the planets in our solar system.  Got it?  Well, now listen to this.  The absolutely nearest star to us, other than the sun, is so far away that light takes more than FOUR YEARS to reach it.  Think about how far that is.  Seriously, dude.  Hundreds of times farther away than the farthest planet.  Thousands, actually.  And that's to the CLOSEST star.

Most stars, in the constellations we see, tend to be a few dozen, a few hundred, or (less often) sometimes a few thousand light years away from Earth.  (A light year is the distance that light, travelling at 186,282 miles per second, travels in one Earth year).

So, that's how far away those stars are.  They are basically ALL located in our galaxy.  There are a tiny number of exceptions, but these exceptions are not just single, individual stars.  They are entire galaxies.  The Andromeda galaxy is a good example.  It is approximately 2.5 million light years away.  You can see it in the constellation Andromeda.

But as a rule, every star you see, every star which IS an actual star, and not a whole galaxy, is indeed located within the Milky Way.

I hope this is helpful.  Please e-mail me back, if you want me to be more clear.  This evening, in about 7 hours, at 9:00 PM Eastern Standard Time, I will be on a computer terminal at a library, which will make is easier for me to include links to URLs.  It's hard to explain, but this computer I'm at is an old piece of garbage, and I can't cut and paste NASA links like I usually try to do.  So, if you want more info, get back to me later.  Otherwise, just try to... Keep...

Looking...

Up!

--Ed