ASTR 3 Lecture Notes - Lecture 8: Metallic Hydrogen, Planetesimal, Tidal Acceleration
Document Summary
Jupiter and saturn are made mostly of hydrogen and helium. Gravity too weak to compress its interior to the extreme temperatures and densities. Planetesimals massive gravity draws in hydrogen and helium gas surrounding them needed for nuclear fusion. Jovian planets made mostly of hydrogen, helium, and hydrogen compounds. Differ in relative proportions of hydrogen compounds. Solid particles that condensed farther from the sun should have been more widely spread out than those condensed nearer to the sun locker to accrete into large, icy planetesimals. As nearest jovian, jupiter is first to get planetesimal large enough for gravity to start. Planets stop accreting gas at same time so distant planets have less time to capture gas drawing gas. Saturn is less dense than uranus or neptune. Uranus and neptune made more of hydrogen compounds, rock, and metal than hydrogen and helium gas. Jupiter is only slightly larger than saturn in radius but 3x as massive.
