(Submitted May 20, 1998)
Why are the densest planets closest to the Sun?
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)
Koji Mukai & Karen Smale
for Ask an Astrophysicist
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