Expert: Jayendra Upadhye - 4/26/2004

Question
What's the color of the milky way?

Answer
Hello Natalie,
The milky way as one would presume is not of one single color as it is not a single unitary object but a composite body made up of many stars.
These vary in age and size.
Stars appear to be of different color depending on their age and size.
So the milky way would appear more red in the center where the old stars and globular clusters with big populations of old stars reside.
The arms with their hot young and large blue stars would be more blue and throughout its body would be the yellow of the common place stars that make up its bulk, stars like our sun.
Hope that puts the matter in perspective.
Thumb rules are:-
1 - The spiral arms of galaxies have young and blue and large stars with very short lives (some 100 million years before they end as supernovas and are gone.)
2 - The galactic cores are richer in globular clusters and old stars that are redder but with longer lives.
3 - The galaxy is pervaded by common stars like the sun that are yellowish and with very long lives. (our sun has gone around the galaxy about 20-22 times with one round lasting about 250 million years.)
Lastly natalie it all depends on where you are when you look at it!
If you happen to be looking edgewise, the huge amount of intervening dust in the spiral arms scatters the light and you see a reddder color. (even making things go pitch black! read about the visible coal sack dark nebula in the southern skies if you can at http://www.seds.org/messier/xtra/ngc/coalsack.html)
If you look at the milky way along the axis of rotation, then all foregoing holds true.
Jayen