Tuesday, September 11, 2007

The Universe

Well, I've covered all nine planets, the moon, sun, and comets in previous posts here. Time to move on to the rest of the Universe. If you're interested in this sort of thing, check out Astronomy: A Visual Guide, by Mark A. Garlick.

Or just check it out here for free...

Between the orbits of Mars and Jupiter lies a cosmic trash pile. This is the realm of asteroids: chunks of metal and rock, battered and ancient, all but the very largest irregular in shape. Some are just tiny pebbles, others as large as entire countries. These fragments are leftovers from the formation of the Solar System, roughly 5 billion years old. The largest asteroid is Ceres, 1000 km across, was discovered in 1801.
The asteroids never formed a single planet because the gravity of nearby Jupiter tugs at them and keeps them from sticking together.

The Kuiper Belt:
Pluto is the farthest planet from the Sun, but it does not mark the edge of our Solar System. Here we encounter the most extensive region, the Kuiper Belt: home to comets and other inert materials on the fringes of interstellar space. Noted astronomer Jan Hendrik Oort discovered this realm, where comets reside for most of their lives, only rarely entering the inner Solar System. This vast, frozen reservoir may be as much as 2 light years wide, and is home to millions of inactive comets.

Stars are vast spheres of gas, so massive that they are constantly in danger of collapsing under their own weight. This inward force is balanced by the presence of nuclear reactions in their cores. This balance keeps stars burning for tens of millions of years. A star's color depends on how hot it is, and their sizes vary enormously.
Around half the stars in our Milky Way galaxy are binaries: twin stars orbiting around a common center of gravity as if tied by an invisible tether. As one star passes in front of another as seen from Earth, varying the total light output, the stars appear to "twinkle".


Jason said...

I've always enjoyed your posts on astronomy, and I apologize for not saying so before now.

A week or so ago I found Hubblecast--videocasts about various things the HST has discovered during its lifetime. Some of the videos are in HD and Dr. J's accompanying narration makes it easy for a layman like myself to understand what I'm seeing.

Anyway, they're under the Videos tab at spacetelescope.org.

Hansisgreat said...

Thanks for sharing, Jason. I checked out some Hubble shots. They are pretty cool.
There's $80M well spent!
I appreciate the tip, and will mention your link in the next "Astronomy" post, if that's ok.

Jason said...

Post away. Looking forward to reading it.