Solar system?
Question:
How can Neptune be smaller in size that Uranus yet be more massive?
Answer:
Some five billion years ago (give or take), the rotating solar nebula flattened into a disk of material that would eventually form the planets. Because the planets formed from a rotating disk, all the planets’ orbits ended up in pretty much the same plane—i.e., the solar system is flat.
And Neptune can be smaller than Uranus but heavier for the same reason that a small chunk of iron can be heavier than a larger piece of, say, wood. Iron is denser than wood, and Neptune is denser (on average) than Uranus.
Ryan Wyatt
Rose Center for Earth & Space
New York, New York
It gave the planets that formed from it their orbital motion.
The same way that a bowling ball can be heavier and also smaller than a beach ball, because it is denser.
Density is mass / volume. The Neptune / Uranus disparity is a less extreme example, of say, comparing the Earth to a neutron star with an equal Earth volume. No basic laws are broken there either.
The rotation set the planets in motion all in the same direction. It also made the nebula flatten out into a disk which explains why all of the planets are more or less on the same plane (not a lot of tilt in their orbits).
Neptune is more dense than Uranus, so it can have less volume yet be more massive. (Density = mass/volume) It is just more compact.
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