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The Question

(Submitted May 20, 1998)

Why are the densest planets closest to the Sun?

The Answer

It is because of the temperature gradient that was in the solar nebula, from which the planets formed. The inner (hotter) parts could only condense out the silicates, forming the terrestrial planets. The cooler part further out could condense out the more volatile compounds, forming the Jovian (or gas) planets.

Best wishes,

Koji Mukai & Karen Smale
for Ask an Astrophysicist

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Last Updated: Thursday, 01-Dec-2005 13:58:39 EST