More than 5 billion years ago, the atoms and molecules that now make up the planets -and our own bodies- were dispersed in a gigantic cloud of dust and gas. A study of the beginnings of the solar system is interesting as an example of the way science in general (and astronomy in particular) progress, because the theory is still in its early development and many gaps remain. The search for answers here resembles a mystery story where there are many clues; new ones appear all the  time and some of the clues seem to contradict others. There are two main categories of competing theories to  explain the origin of the solar system: evolutionary theories and catastrophe theories. I examine the evidence for each and show why
one is gaining favor among astronomers.

What the data tell us?
Any successful theory of the solar system’s origin must explain the patterns exhibited by its members and should also be able to account for exceptions to the patterns. Here is a list of significant data that must be explained.
1. All of the planets revolve around the Sun in the  same direction (which is the direction the Sun rotates),
and all planetary orbits are nearly circular.
2. All of the planets lie in nearby the same plane of revolution.
3. Most of the planets rotate in the same direction as they orbit the Sun, the exceptions being Venus and Uranus.
4. The majority of planetary satellites revolve around their parent  planet in the same direction as the planets rotate and revolve around the Sun. In addition, most satellites’ orbits are in the equatorial plane of their planet.
5. There is a pattern in the spacing of the planets as one moves out from the Sun, with each planet being about twice as far from the Sun as the previous planet.
6. The chemical compositions of the planets have similarities, but a pattern of different also exists, in that the outer planets contain more volatile elements and are less than the inner planets.
7. All of the planets and moons that have a solid surface show evidence of craters, similar to those on our Moon.
8. All of the Jovian planets have ring systems.
9. Asteroids, comets, and meteroids populate the solar system along with the planets, and each category of object has its own pattern of motion and location in the system.
10. The planets have more total angular momentum than does the Sun, even though the Sun has most of the mass.
11. Planetary systems in various stages of development exist around other stars.

Sources : In Quest of the Universe; T. Koupelis & K. Kuhn.

Tags: Astronomy is more than

This entry was posted on Sunday, June 14th, 2009 at 5:00 pm and is filed under Astronomy, English, Personal, free. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.