Star Life Cycles - Planetary Systems

Stars and Nebulae

Index

Interstellar Clouds
Classes of Objects
Gas Giant Planets
Brown Dwarfs
Red Dwarfs
Sun-sized Stars
Large Stars
The Largest Stars
Impossible Stars
Star Clusters
Planetary Systems
Rocky Planets
An Endless Cycle

Questions
Credits
Links
Michael Gallagher
August 2002
July 2007

Planetary Disk - Frame from the TV Series Universe, Program 4 The Planets

When interstellar clouds condense, rotating disks of gas form around central stellar masses. Planets form in the disk, away from the central stars.

The oldest rocks found are from the Moon and the asteroids. They are 4.7 billion years old. That tells us that the Solar System formed 4.7 billion years ago.

Until 1995, the only planetary system we knew of was our own. In July 2007, 230 planets have been discovered in orbit round nearby stars. Planetary systems appeat to be common in the galaxy.