According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
A) The colder gas in the outer regions of the solar nebula had less gravity and therefore could not gather up into such large balls as it could closer in.
B) Ices were able to condense at the distance of Jupiter and Saturn, but only rock and metal could condense at the distances of Uranus and Neptune.
C) Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
D) The size differences are thought to be a random coincidence.
Question 2
A main-sequence star's luminosity can directly inform us of
A) the star's radius.
B) the rate at which it converts hydrogen to helium.
C) the star's mass.
D) the star's distance from us.
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