Our galaxy is filled with giant planets. Astronomers have already discovered hundreds of them, and they expect to find perhaps thousands more over the next few years. These worlds are many times bigger and heavier than Earth, and many of them are bigger than Jupiter, the giant of our own solar system.
There may be two recipes for brewing up such giants.
The first recipe calls for adding the ingredients slowly. Small bits of rock and ice come together to form planetesimals -- solid bodies that are the size of small mountains. The planetesimals then stick together to form the cores of the giant planets. When they grow big and heavy enough, these solid cores pull in vast amounts of gas left over from the formation of their parent stars, so the planets grow to giant proportions.
This recipe is generally considered the leading contender. In part, that's because a planet can form either close to the star or farther out, and because the process can happen quickly or slowly, providing more time to make planets.
The other recipe works only for planets that are far away from their stars. In this model, dense lumps in the material around a newborn star collapse to form planets. It's basically a one-step process -- you don't have to make little objects before you make big ones.
It's possible that both methods are at work -- giving birth to giant worlds throughout the galaxy.
More about building solar systems tomorrow.
Script by Damond Benningfield, Copyright 2010
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