Which of the following is the best description of the formation of a giant planet with a massive core? (at least as described in the lectures!)1 pointPlanetesimals grow through gravitational focusing. Dynamical friction slows the motions of the largest objects leading to runaway growth of oligarchs, which are isolated from other nearby oligarchs. Gas slowly accretes onto the oligarch through an envelope until the pressures are too high to support the envelope and massive amounts of gas collapse making the gas giant.Planetesimals grow through gravitational focusing. Dynamical friction slows the motions of the largest objects leading to runaway growth of oligarchs, which are isolated from other nearby oligarchs. Large numbers of oligarchs merge over hundreds of millions of years, leading to a giant core.Gas slowly accretes onto the oligarch through an envelope until the pressures are too high to support the envelope and massive amounts of gas collapse making the gas giant.Planetesimals grow through gravitational focusing. Dynamical friction slows the motions of the largest objects leading to runaway growth of oligarchs, which are isolated from other nearby oligarchs. The gravitational pull of the oligarch quickly overcomes the rotational and pressure forces from the disk, causing rapid growth of the gaseous atmosphere.In a massive disk the force of gravity in a patch of the disk overcomes the pressure and rotational forces and the patch quickly collapses into a giant planet. The heavy materials sink to the bottom and form the core.Planetesimals grow through gravitational focusing. Dynamical friction speeds the motions of the largest objects leading to more frequent collisions and runaway growth of oligarchs, which are isolated from other nearby oligarchs. Gas slowly accretes onto the oligarch through an envelope until the pressures are too high to support the envelope and massive amounts of gas collapse making the gas giant.

Which of the following is the best description of the formation of a giant planet with a massive core? (at least as described in the lectures!)

8.Question 8Isolation mass is another key concept in understanding the formation of planetesimals and eventually planets. We sometimes use the term "oligarch" to describe a body which has become isolated. Which of the following statements about isolation mass is false?1 pointDynamical friction causes the oligarchs to slow each other downOligarchs get more massive futher out in the diskWhen an object reaches isolation mass it stops growing rapidly by gravitational focusingAll of these statements are trueIsolation masses are much higher outside of the ice lineOligarchs are space further and further apart further out in the dis

3.Question 3Which of the following is NOT required for the formation of a large nearly isotropic Oort cloud full of many small bodies, assuming the scenario that we discussed is the dominant mechanism? 1 pointA planet like Jupiter which is massive enough to scatter bodies out of the solar systemPassing stars which perturb the orbits of low perihelion, high semimajor axis objectsA smaller planet like Neptune to scatter icy bodies inward so they can be ejected by a more massive planet like JupiterA population of small bodies which is close enough to a planet to get scattered outwardMultiple stellar encounters to randomize the cometary orbits into an isotropic cloudAll of these are required

4.Question 4The terrestrial planets appear to have taken much longer to finally assemble than the gas giants did. Which of the following statements about these timescale is NOT true?1 pointOne reason that the gas giant formation timescale is thought to be so fast is that we do not observe stars to have gas around them after they are ~3 Myr oldWe can learn about the timescale of terrestrial planet differentiation by looking at isotopic ratios of hafnium and tungsten.Oligarchs form very quickly through runaway growth but because they are gravitationally isolated it takes a long time for them to assemble into larger bodies.Mars differentiated quickly, so tungsten-182, the radioactive decay product of hafnium, is abundant in Martian meteorites.All of these statements are trueGrowth of the terrestrial planets was slowed by the rapid growth of the gas giants, which caused oligarchs to have have velocities and break apart

Which of the following statements is not a description of Neptune? Known for its strongest winds Has no atmosphere One of the gas giant planets Has moons