There are many popular misconceptions concerning the size and scale of
objects in the Solar System. These mostly have to do with a failure to realize
the relative radii of planets and the Sun, and the failure to appreciate how
large the outer solar system is relative to the inner solar system.
The Relative Radii of the Sun and Planets
The Sun and the gas giant planets like Jupiter are by far the largest objects in the Solar System. The other planets are small specks on this scale, as the following figure illustrates.
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| The Sun and planets drawn to scale |
Indeed, on this scale the smaller planets like Pluto and Mercury are barely visible.
Masses and Densities
The masses of the planets are also concentrated in the Gas Giant planets Jupiter, Saturn, Uranus, and Neptune, as the following graph indicates.
However, the large mass of these planets comes from their absolute sizes, not their densities. The inner planets are by far the most dense, as the following graph indicates:
This distribution of masses and densities in the Solar System is a key observation that a theory of the origin of the Solar System must explain.
Information supplied by: http://csep10.phys.utk.edu