Here’s another great post from the Bad Astronomy Blogger: 10 Things You Didn’t Know About the Milky Way.
My Favorite Unknowns (ok so actually I knew them but BAB certainly states them nicely)? Numbers 6 and 7:
“6) You can only see 0.000003% percent of it.
When you got out on a dark night, you can see thousands of stars. But the Milky Way has two hundred billion stars in it. You’re only seeing a tiny tiny fraction of the number of stars tooling around the galaxy. In fact, with only a handful of exceptions, the most distant stars you can readily see are 1000 light years away. Worse, most stars are so faint that they are invisible much closer than that; the Sun is too dim to see from farther than about 60 light years away… and the Sun is pretty bright compared to most stars. So the little bubble of stars we can see around us is just a drop in the ocean of the Milky Way.
7) 90% of it is invisible.
When you look at the motions of the stars in our galaxy, you can apply some math and physics and determine how much mass the galaxy has (more mass means more gravity, which means stars will move faster under its influence). You can also count up the number of stars in the galaxy and figure out how much mass they have. Problem is, the two numbers don’t match: stars (and other visible things like gas and dust) make up only 10% of the mass of the galaxy. Where’s the other 90%?
Whatever it is, it has mass, but doesn’t glow. So we call it Dark Matter, for lack of a better term (and it’s actually pretty accurate). We know it’s not black holes, dead stars, ejected planets, cold gas — those have all been searched for, and marked off the list — and the candidates that remain get pretty weird (like WIMPs). But we know it’s real, and we know it’s out there. We just don’t know what it is. Smart people are trying to figure that out, and given the findings in recent years, I bet we’re less than a decade from their success.”
And all of that is pretty astonishing. What little we do so see is so incredibly beautiful –
Here’s a photo-sketch I took in WI, of the Milky Way. And even this shot is more sensitive and includes more detail than what the naked eye can perceive:
As an artist, who paints imagery on the triple-basis of observation, representation and illusion, it is exciting to be living in a time when what we can know about the universe is vastly greater than what we can see, that there’s always more than meets the eye that we can indeed verify, measure, and assess. The visual artist can include the invisible; blindness enhances vision.