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CALTECH GE 133 - Planetary Formation & Evolution

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Ge 133 – Planetary Formation & EvolutionFinal ExaminationOut: 02 December 2011Due: 09 December 20111 pmThis exam has a 4-hour limit and must be completed within a single block of time.It is totally closed book, notes, friends, neighbors, internet, dogs, cats, pygmy hedgehogs,etc. More seriously, the time limit i s there mostly so that you are forced to finish, we don’tthink it should t ake you nearly this long.The problems are worth 10 points each (so the individual parts of problem o ne areworth two points each, etc.).Good l uck!1. Order of Magnitude (Exo)Planetary ScienceTo order of magnitude, give the following quantities, and briefly, briefly, brieflydescribe the evidence or theory used to constrain them:• C/H ratio (by number) in the Interstellar Medium• The mass of a Gi ant Molecular Cloud.• The va lue of the α disk viscosity parameter required to explain disk l ifetimes.• Migration timescale of Jupiter if it opens a gap in the surrounding disk.• Formation of FeNi cores in differentiated bodies & the final accumulation of terrestrialplanets.2. Extrasolar PlanetsThere are four “major” methods for detecting extrasolar planets – radial velocitysurveys, transit surveys, direct imaging, and mi crolensing (astrometric surveys mayultimately yield a large number of detections, but we didn’t cover this technique in t he classvery well, so we’ll let you off the hook there). Compared to radial velocity (or astrometricsurveys) alone, what further information about extrasolar planets can be extracted fromtransit measurements, especially if radial velocity data are also available? What wavelengthregions are most important for extracting exoplanet physical properti es?3. Disks and the Young Stars they EncircleMost cirucmstellar disks have never been imaged, and so we learn about them in waysakin to the parable of the blind men describing an elephant – from diverse lines of evidence.What do each of these features tell us about an individual circumstellar disk/young starin which they are seen: UV ex cess, lithium features in stellar photospheres, infrared excess(say, 1-30 µm), silicate emission features, millimeter-wave (excess) flux. How are diskevolution time scales obtained? Agai n, you can/should be brief!4. Planetesimal GrowthWhat are the factors that can affect the velocity evolution of a planetesimal swarmand thus the formation of planetary embryos? Explain whether each effect increases ordecreases the velocities/veloci ty dispersion. What effect dominates?5. The Core-Accretion PictureIn the core-accretion model of Jovian planet formation, what are the major phases inthe transformation of sub-micron sized dust grains into a full fledged planet? Why in sucha model do Jov ian planets form in the outer regi ons of forming planetary systems?6. Planetary Migration?What is the evidence that migration occurred in at l east some extra-sola r planetarysystems? What is the physical mechanism by which such migration might have occurred,and what determines the different migration rates of the so-called Type I & II scenarios?7. Gas dissipationDescribe the different ways in which the gaseous component of the circumstellar diskdissipates. Where in the disk is each of these most important? For extra credit, are theirtracers that could realistically be used to examine these processes (in the solar system orastronomically) with current instrumentation?8. Our Own Kuiper BeltSketch the eccentricity-major axis distribution for detected Kuiper Belt Objects(KBOs). Expla in how we think each of these major features came to be, starting from aplanetesimal disk in which Neptune is embedded. Why is Sedna so different from all otherknown KBOs?9. Other Kuiper Belts?For a planet orbiting a central star, how many Lagrange points are there? Which ofthese have stable orbits near them? Why do we care about these Lagrange points in theanalysis of the debris disks around young main-sequence stars? Be sure to include in yourargument the lifetime of ∼micron-sized dust particles in such systems.10. Meteorites and the Young Solar EnvironmentFrom what materials do chondritic meteorites take their name? What are CAIs?From what region(s) of the solar system are meteorites delivered to the Earth? What canwe learn about the solar nebula from such materials, and what lines of evidence are therethat suggest the Sun may have formed in a young stellar cluster as opposed to relativeisolation? What time scales are inferred? Are there processes in the pre-solar nebula thatcan confuse these putative

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