133 Ge Planetary Formation & Evolution
Final Examination
Out: 02 December 2011
Due: 09 December 2011
1 pm
This 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 is there mostly so that you are forced to nish, we dont
think it should take you nearly this long.
The problems are worth 10 points each (so the individual parts of problem one are
worth two points each, etc.).
Good luck!
1. Order of Magnitude (Exo)Planetary Science
To order of magnitude, give the following quantities, and briey, briey, briey
describe the evidence or theory used to constrain them:
C/H ratio (by number) in the Interstellar Medium
The mass of a Giant Molecular Cloud.
The value of the disk viscosity parameter required to explain disk lifetimes.
Migration timescale of Jupiter if it opens a gap in the surrounding disk.
Formation of FeNi cores in dierentiated bodies & the nal accumulation of terrestrial
planets.
2. Extrasolar Planets
There are four major methods for detecting extrasolar planets radial velocity
surveys, transit surveys, direct imaging, and microlensing (astrometric surveys may
ultimately yield a large number of detections, but we didnt cover this technique in the class
very well, so well let you o the hook there). Compared to radial velocity (or astrometric
surveys) alone, what further information about extrasolar planets can be extracted from
transit measurements, especially if radial velocity data are also available? What wavelength
regions are most important for extracting exoplanet physical properties?
3. Disks and the Young Stars they Encircle
Most cirucmstellar disks have never been imaged, and so we learn about them in ways
akin 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 star
in which they are seen: UV excess, lithium features in stellar photospheres, infrared excess
(say, 1-30 m), silicate emission features, millimeter-wave (excess) ux. How are disk
evolution time scales obtained? Again, you can/should be brief!
4. Planetesimal Growth
What are the factors can that aect the velocity evolution of a planetesimal swarm
and thus the formation of planetary embryos? Explain whether each eect increases or
decreases the velocities/velocity dispersion. What eect dominates?
5. The Core-Accretion Picture
In the core-accretion model of Jovian planet formation, what are the major phases in
the transformation of sub-micron sized dust grains into a full edged planet? Why in such
a model do Jovian planets form in the outer regions of forming planetary systems?
6. Planetary Migration?
What is the evidence that migration occurred in at least some extra-solar planetary
systems? What is the physical mechanism by which such migration might have occurred,
and what determines the dierent migration rates of the so-called Type I & II scenarios?
7. Gas dissipation
Describe the dierent ways in which the gaseous component of the circumstellar disk
dissipates. Where in the disk is each of these most important? For extra credit, are their
tracers that could realistically be used to examine these processes (in the solar system or
astronomically) with current instrumentation?
8. Our Own Kuiper Belt
Sketch the eccentricity-major axis distribution for detected Kuiper Belt Objects
(KBOs). Explain how we think each of these major features came to be, starting from a
planetesimal disk in which Neptune is embedded. Why is Sedna so dierent from all other
known KBOs?
9. Other Kuiper Belts?
For a planet orbiting a central star, how many Lagrange points are there? Which of
these have stable orbits near them? Why do we care about these Lagrange points in the
analysis of the debris disks around young main-sequence stars? Be sure to include in your
argument the lifetime of micron-sized dust particles in such systems.
10. Meteorites and the Young Solar Environment
From 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 can
we learn about the solar nebula from such materials, and what lines of evidence are there
that suggest the Sun may have formed in a young stellar cluster as opposed to relative
isolation? What time scales are inferred? Are there processes in the pre-solar nebula that
can confuse these putative signatures?