Ge/Ay 133: The Formation and Evolution of Planetary
(INCREASINGLY LESS) NEW: Glossary of Terms
Profs: Geoff Blake
165A S. Mudd
TA: Joshua Kammer
158 S. Mudd
Office hours: M/W 4-5 p.m., 158 South Mudd
Geoff is also the Master of Student Houses (MOSH), and so splits his time between S. Mudd and
his office on the Olive Walk. E-mail is the best way to get a hold of him!
These web pages are currently under construction, so tune in regularly
during the first week+ of class, esp. for class dates and reading.
Class hours: MWF 10-11 am
Class location: 176 S. Mudd
(You might want to read this, important information here!)
Week 1: Introduction to the solar system, exoplanet detection techniques.
Week 2: Properties of other planetary systems.
Week 3: Star formation; stars with disks.
Week 4: Physics of viscous accretion disks, growth of dust to planetesimals.
Week 5: Formation of terrestrial and giant planets.
Week 6: Disk dissipation/lifetime, Solar formation environment?
Week 7: Solar system dynamics, especially the small bodies in the outer solar system.
Week 8: Small bodies in the outer and inner solar system.
Week 9: Exo-Kuiper and Zodiacal Belts (short week, Thanksgiving).
Week 10: Additional solar system constraints, wrapping up.
As they are posted, you can download any slides from the lectures here
The main textbook for the course, Astrophysics of Planet Formation, by Phil Armitage,
does a very good job of covering the essential aspects of disk evolution and the various stages of planet formation.
But, it does not deal with all of the aspects of planet formation that we will be considering, and so
additional reading will often be assigned. Central papers are listed below in
italics, and we'll often include additional items of interest you
can take or leave as you see fit. I have also just discovered the nice book
entitled Exoplanets, edited by Sara Seager, which has very nice tutorial chapters on all the major methods of exoplanet detection. I have the one copy from the GPS library and will look into getting an extra copy or two for the class. Geoff's travel schedule for Oct/Nov is not yet set, and there will certainly be NSF-related trips upcoming. Thus, the schedule below is iffy after the first couple of weeks of class. Stay tuned.
Monday, 26 September: Pages 1-14 of Armitage provide a short introduction to various
important properties of the solar system. For more detailed reading,
The solar system
and its place in the galaxy. is a nice (but long!)
introduction to what is in the solar system. You need only read sections I
and II, though III and IV make interesting introductions to the remainder
of the class. There are many textbooks one can consult nowadays, one of the
more readable is The New Solar System, edited by Beatty, Petersen, and
Chaikin (Sky Publishing).
For reference, here is the classic paper on binary star distributions
from Duquennoy and Mayor that presaged
many of the results to come on extrasolar planets. For a true classic,
try Kant's 1755 attempt at describing the universe and its origin. Laplace has his say
a few years later. Finally, for those with an interest in planetary
astronomy and the sometimes rocky history of science, the
discoveries of Neptune and Pluto make
for an interesting story.
Wednesday, 28 September: How can we detect extrasolar planets?
Here you should consult pages 15-29 of Armitage.
For a look back at how things have developed, a now rather dated but still detailed
look at the possibilities before the onslaught of actual detections can be found in the
Towards other planetary
systems. report written in NASAese a few years before
the discovery of the first extrasolar planets. It is a long
report, but you only need read the following sections: 3.1, 3.2 through
The potential role of ground-based astrometry in TOPS ; 3.3; 3.4; 4.1 -
4.4 to get a sense of things. I will work on making a smaller file with just the pages necessary.
What we'll concentrate on is the potential discovery space with indirect
techniques, as summarized in Figure 3.1. So, think a bit about
this figure and the pages that follow.
A glossier draft of the 2006 roadmap from NASA that is primarily
meant for public policy makers can be found
here, which updates the
planet detection story/strategies and which does have a decent
listing of the sometimes bewildering array of upcoming and potential
NASA/ESA missions related to exoplanetary science near the end. Chapter 5
is most relevant to today's discussion, but I include Chapter 4 and the
technology roadmap for completeness and those interested. I will update
these files with additional suggested chapters/reading from the Exoplanets book over the next few days.
Friday, 28 September: The architecture of extrasolar
planetary systems. I. A short overview of the statistical properties of
extrasolar planetary systems is provided in pages 29-33 of Armitage, and
there is no shortage of review articles here. For example,
of extrasolar planets ; is a review with most of the important
known properties of extrasolar planets as derived from radial velocity
studies. Here is a more
from our own John Johnson that
covers transit-based results as well.
This field is moving very quickly,
and so if you are interested in keeping up-to-date you should peruse
http://exoplanet.eu or one of the
other extrasolar planet web sites on occassion! For information junkies,
I recommend the
Exoplanet Data Explorer, where you can
get up to the date information and make plots of all sorts of things like
the mass distribution, orbits, eccentricities, and the like for the
presently known exoplanets. Recent topics of
interest in extrasolar planet research that we'll think about include
the stellar metallicity/planet correlation (see Marcy review
above) and the discovery of a "super-Earths" toward several systems,
especially those around M-type stars (such as GJ 1214b).
NEW!!! A summary of the HARPS survey has just been posted on astro-ph,
and announces a nearly 50
percent detection rate for planets in orbits up
to only 100 days!
Monday, 03 Oct: The architecture of extrasolar planetary
systems. II. The rare cases where extrasolar planets
transit in front of their stars tell us a great deal about them. For
an excellent review of the practice and science of exo-planetary science,
see the recent review
by Josh Winn (MIT).
An interesting case study is presented by the
super-Earth core to a Jovian planet.
Diagrams of the proposed interior structure of this `hot Saturn' and
its comparison to Jupiter may be found at
IR observations of
the `secondary eclipse' of transiting planets by their stars
have resulted in the first detection of the
from an extrasolar planet. The impressive pace of advancement
with Spitzer observations is apparent in the report of the full
of an extrasolar planet less than two years later. Finally,
for a summary of the over 1000 planet candidates from the first
few months of the Kepler mission, point your browser
Wednesday, 05 Oct: What else can you learn from transits?
These events also provide the best opportunity
to characterize the atmospheres of extrasolar hot Jupiters, as is
described in the nice work using HST NICMOS on
Direct imaging of planets has a now reasonably lengthy history of
announcments followed by retractions, but the late-2008 detections
of co-moving and apparently orbiting companions to
HR 8799 and
may herald the opening of the floodgates.
Friday, 07 Oct: Another area likely to see significant growth
in future years is microlensing. We'll go over the
basics of the technique
in this lecture, and look into possible future missions/searches. While
follow-up is not possible in this case, microlensing offers the immediate
ability to search for Earth-mass
planets in the so-called habitable zone (white paper to the Asro2010
Monday, 10 Oct: From molecular
clouds to stars. The basics of star formation. Gotta have stars
if you're gonna have planets, unless they are free floating, of course. To
get a feeling for how dynamic this process is, the beautiful simulations
Matthew Bate at the University of Exeter are hard to beat!
Wednesday, 12 Oct: Young circumstellar
disks and their evolution: a review . This review examines
the properties of circumstellar disks and how they evolve. Over the next
couple of weeks, the Armitage text will cover the physics of disks nicely, but
not the observational constraints on disk structure and evolution.
On larger spatial scales, for example, outflows from young stars play a pivotal role in the
evolution of molecular clouds, yet are not well understood. We'll come
back to outflow models when we talk about meteorites and the early solar
system, for now I have mounted the
Protostars & Planets V
prerpints for your convenience. There are several articles on disks and outflows
here. For the latter, the observational papers by Bally (optical/IR approaches) and Arce
(mm-wave and radio techniques) are the most accessible. Skim them to get
a feeling for what can and cannot be learned at present.
Friday, 14 Oct: Disk statistics and timescales.
Imaging disks is hard, and so much of what
we know about them comes from spatially unresolved measurements of
their Spectral Energy Distributions, or SEDs. Interpreting these
has become an ever-more complex art, and pages 36-47 of Armitage are
a good place to start your reading. For peer-reviewed treatments with
varying levels of sophistication, the paper by
Chiang and Goldreich
is the classic reference.
This is an extensive, and dense paper, so concentrate only on sections
1 and 2, and take a quick look at section 4 through 4.1.3 on spectral
features in the infrared (see also the remaining sections of Chapter 2
in Armitage, which provides
a more extensive derivation of many of the formulae in Chiang and Goldreich).
Finally, images in optically thick
lines can provide access to
the disk velocity fields, inclincation, etc. This is a terse paper,
so mainly think about why the emission patterns in Figure 1 have
the shapes that they do! The most appropriate PP V review is that
by Dullemond et al.
Such observations are possible for only a handful of objects. So,
most of our information on dissipation timescales comes from
observations of the dust. At millimeter-wavelengths, a
good paper to start with is:
A survey for circumstellar
disks around young stellar objects, This is an update of
the classic early paper by Beckwith and
The goal is to learn something about the masses of the detected
disks. There is a lot of detail you don't need here, so concentrate on
the motivations for this kind of work and why long wavelengths give
access to the disk mass. By combining optically thick and optically
thin tracers of the disk, astronomers can investigate the
timescales associated with disk dispersal. Lynne Hillenbrand
has written an updated account of
disk dissipation time scales and
how they can be assessed.
Monday, 17 Oct:
OK, here's where it all happens. First we need to think a bit more
deeply about the structure and transport properties of circumstellar
disks. We will use primarily the Armitage text, Chapter 3,
but the older Formation of Planets
review by Steven Ruden has some good material as well.
The latter review is nice, but terse in places, so I'll append to
the various days some additional peer-reviewed articles. These are
often quite dense and specialized. I do not expect you to read them
in detail, but provide them so that if you are interested in such
processes and topics you have a place to get started. For today's
discussion, what we really care about is the overall structure and
transport in the disk. For today, it's pages 68-87 of Armitage (and
up to section 3 of Ruden).
One interesting discussion about the possible
impact of magnetic fields on disk transport that is outlined in Armitage
was first raised in this
article on layered accretion.
There are also several relevant chapters in the Protostars and Planets
V preprint proceedings mounted on the class web site that you can
peruse at your leisure.
- Wednesday, Friday 19, 21 Oct: Geoff on NSF travel.
Monday, 24 Oct: Now that we've looked at "basic" disk physics,
we need to think about how dust grows into planetesimals. This is described
in the beginning of Chapter 4 of Armitage (through section 3 of Ruden).
Recent simulations of such processes suggest
rapid growth and sedimentation in
disks is likely unless collisions regenerate small dust grains, but we'll
see there are serious issues in getting up to >km size scales. Recent
theoretical work has suggested a possible "out" by using turbulence to
directly bypass the meter-sized `migration barrier,' as is described
in the simulations by
Johansen et al.
Wednesday, 26 Oct: How do we grow larger bodies? Gravitional
interactions are the key here, as discussed in Chapter 5 of Armitage
(and through the end of section 4 in Ruden). The processes by which
oligarchs grow and then interact may be found in this article by our
own Peter Goldreich and Re'em Sari.
Friday, 28 Oct: Gas giants via core-accretion and disk
instabilities. Go through Chapter 6 of Armitage.
A nice analytical analysis of the core mass needed to drive gas accretion
can be found in Stevenson 1982, Planet. Space Sci. 30, 755-764.
This is not available electronically, so
here is a scanned version.
A rather more pedagogical discussion can be found in section III.C. of
the Armitage notes, and I have posted to recent articles by Jack Lissauer
and colleagues on dust
settling and core-accretion timescales followed by the role of gap
formation and angular momentum in the
formation of Jovian
satellite systems. Finally,
we're not going to talk much about disk instability models in this
class, but in the interests of full disclosure Alan Boss's
recent 3-D simulations of this
process and it's likely dependence on metallicity, etc. are worth a look.
The paper cited is lengthy with lots of figures, but the overview of
instability versus core-accretion models, hot Jupiter formation, and
the like is worth a skim.
Monday, 31 Oct: Planet migration. For this lecture, the appropriate
Armitage section is 7.1. Here, since we are
dealing with planet-disk (and planet-planet) interactions, I have mounted
some nice animations
of gap formation and planet migration from
Masset's planet formation/simulation pages. For those interested
in the gory fluid dynamics details, here's an ApJ article
formation/Linblad resonances. The appropriate review notes are
section IV.A. of Armitage. Many of the analyses
of migration that find high rates use linearity assumptions. For
a recent simulation that may well offer a more realistic model,
point your browser here.
Wednesday, 02 Nov: Planet-disk interactions and migration,
Friday, 04 Nov: Find out about
gas dissipation and migration. What might this say about Uranus
and Neptune? Other sources of information about this topic would be
the Dullemond et al. chapter in PP V referenced above, and a recent
paper by Alexander et al.
that compares "toy disk models" of the
photoevaporation process with what is known about disk masses and ages.
See also section 3.6 of Armitage.
Monday, 07 Nov: What about planetary dynamics in our own solar system?
The first of two class sessions on the small body population beyond Neptune
(the Edgeworth-Kuiper belt). The theme here will be observations. A good introduction can be found in
is Mike Brown's Physics Today article which
is (or at least should be) a relatively easy read. The pretty Physics Today
preprint version may be found here. The second Kuiper Belt
also from Mike for the newly minted
Comets II book, goes in to more detail,
so read it second.
Wednesday, 09 Nov: Now we need to think about the formation and destruction of small bodies in the outer Solar System. The dynamical properties of the Kuiper Belt
are strongly influenced by the outer giant planets. A view advanced a
few years ago suggested that
Uranus and Neptune formed
between Jupiter and Saturn.
Friday, 11 Nov: More recent approaches, termed
the Nice model utilizes a crossing
of the 1:2 mean motion resonance of Saturn and Jupiter
that attempts to get around problems with the timescales associated
with the oligarchic growth of cores in the outer solar system and explain
some unusual dynamical properties of the outer solar system. A quick overview
of this model may be found in section IV.B. of Armitage. Our own
Konstantin Batygin and Mike Brown have surveyed the possible gas and ice
giant configurations that are compatible with Nice-like outcomes, as
We'll also talk a bit about the largest icy bodies
known far from home. Here's a link for those interested in learning
more, for example, about the
discovery and implications of the detached KBO Sedna.
Monday, 14 Nov: What about Kuiper belt-like structures around
other stars? We can `see' them through the dust they create. The nearest
and most extended can be imaged, but in terms of statistics and timescales
the best data come from the Spitzer Space Telescope.
A first survey of
(mostly A) nearby stars shows dramatic scatter on top of an overall
decline (for a press release describing this work, point your browser
Concentrate on the Introduction, Figure 1, and the
Discussion. Spitzer has also enabled the first search for Kuiper
belt analogs around systems known
to harbor planets.
Wednesday, 16 Nov: Comets! This paper
on the formation of the Oort cloud and the delivery of comets
goes into more detail than we have time for, so read and understanding
sections 1-3 and take a look at 6-7. Any information comets retain
about their origins is contained in their chemical composition. Here is
a brief review of the volatile
composition of comets, useful mainly for its table of detected
species and references to other reviews. Skim the intro and conclusions.
The Stardust mission has been telling us quite a bit about the dust in
one particular comet. For an overview of what's been discovered to date,
the best place to look is the
Friday, 18 Nov: We're working our way in, so next read
formation and evolution of the asteroid belt. An interesting
update to the kinds of calculations presented here is that
considering the delivery of
water to growing planets and the
habitable zones around stars. This is also the parent body region
for meteorites. More recent, large scale simulations include
a more radical proposal in which the giant planets undergo substantial
radial migration during the gas-rich disk phase, called the
"Grand Tack" scenario (since Jupiter and Saturn first migrate inward,
- Monday, 21 Nov: Student Affairs retreat for Geoff, no class.
Wednesday, 23 Nov:
Chondritic meteorites can give us insight into many details of solar system
formation. But what do they mean??? Here is a short overview of the
ties between chondrites and the disk in which they formed.
Here I have mounted a more thorough, but
introductory review of
chondrite properties and implications. Finally, short-lived
isotopes have much to tell us about the early solar system. When
combined with astronomical observations, this helps us to think
about The cradle
of the solar system, As we saw earlier, the lifetime of disks and the
means by which they are dispersed can depend on their environment. Thus,
the question arisis: Can we determine in what sort of cloud the solar system formed?
The [very] short paper cited above argues that it was not in regions like Taurus
that form primarily Sun-like stars in relative isolation.
This paper is dense with ideas, so please read carefully.
- Friday, 25 Nov: The day after Thanksgiving, Institute holiday.
Monday, 28 Nov: Further solar system constraints.
Thanks to recent Hf/W isotopic studies, our
understanding of the
timescales associated with the formation of the Earth has some
new constraints. The Nature papers that present the raw data on which
this short overview rests may be found
These studies have also illuminted dynmanical simulations of
giant impact the formed the Earth/Moon system.
In this article by Robin Canup (Icarus 168, 433)
it's most important to read the
Introduction and Key Constraints sections. For those interested,
Robin has also written a nice Science article on a
collisional origin for Pluto/Charon.
What does all this mean for the early Earth? What do
planet formation theories tell us about the origin of life? What
defines the so-called "habitable zone"?
Wednesday, 30 Nov: We've been thinking about the dynamics
in our own solar system for a bit, let's revisit extrasolar
planets and think about the potential dynamics that shaped the
observed exo-planetary systems. Perhaps the most unusual is the
first one discovered, Ups And.
For those interested in how such calculations can be used to examine
the stability of and chaos in our own planetary system,
read here. Planet-planet
interactions are discussed in section 7.4 of the
Friday, 02 Dec: Wrapping up. Finish up exo-planetary dynamics
and think a bit about what the future might hold.
Homework (Plese leave homeworks in TA's mailbox, 1st floor of S. Mudd)
Will be updated as class moves along.
- Problem Set 1, due Oct. 6
- Problem Set 2, due Oct. 13
- Problem Set 3, due Oct. 27
- Problem Set 4, due Nov. 3
- Problem Set 5, due Nov. 10
- Problem Set 6, due Nov 17
- Problem Set 7, due Dec. 1
- Final, due Dec. 9