Important Disclaimer - This will hopefully be helpful for studying
for the second test in AST 208, but is absolutely not a substitute
for discussions in class, notes, studying, and thinking.
***now updated for the last few parts since the last test ad
before the final ***
I. Jovian (giant) planets - basic properties (e.g. main elements, basic
structure), how and why they differ from terrestial planets.
II. Rings and moons of Jovian planets -this is where the idea of
tidal force and tidal limits were introduced, as this is both part of
understanding why giant planets have rings, and also understanding
the source of the energy driving the activity on some of Jupiter's
moons.
III. Asteroids, Comets, Kuiper Belt Objects, and Pluto. How the
rest of the stuff in the solar system fits in. What these are
made of, where they are located, and how they orbit. How the
Kuiper Belt is thought to have become the way it is, and
how the solar system from Jupiter outwards has evolved over
time.
IV. Formation of the Solar System (and other solar systems).
Key steps in the formation process, why terrestial vs. giant
planet division, how planets are made, and open questions
in the process.
V. Extrasolar planets (exoplanets). Techniques for finding
them - understanding for how each one works (now including
microlensing), what we have found and how this is affected
by the capabilities of the different techniques. Also a bit
now on how SETI works.
Answers to last few in-class questions
Q. What is Pluto's year compared to Neptune's?
A. The easiest way to do this is to remember that Pluto is in
a 3-2 resonance with Neptune, and that this means Pluto goes
around the Sun two times for every three times Neptune does.
Thus Pluto's year is 1.5 times Neptune's. In the unlikely
case you forgot about the 3-2 resonance, but remembered
Neptune was at about 30 AU and the semi-major axis of
Pluto was about 39 AU, you could use Kepler's law and
get the same answer.
Q. (a) Explain why the doppler technique is better at finding
Jupiter mass planets than Earth mass ones (one or maybe two
sentences should do). (b) Is it easier for the Doppler technique
to find a Earth mass planet closer or farther away from its sun? Why?
The doppler technique is better at finding Jupiter mass planets
because the gravitational force goes as M_planet * M_star/ distance^2,
and it is this gravitational force that makes both the planet
and star move, with the star moving less because F = M a, and
M is bigger for the star. So with bigger M_planet, F_gravity
is stronger, and the doppler shift of the star is greater.
(b) As given above, F_gravity also depends on 1/distance^2, so
smaller distances give larger forces.
One more item is I've linked here to a pdf file I made of the
timescales for different stages of Solar System formation, since
I received some requests for this material.
PDF file of the three slides from class explaining the answer to in
class question 11 about why the Doppler shift can detect planets
to lower masses at smaller distances from their stars, while
astrometric searches have decreasing senstivity to planets of
a given mass at smaller distances from their star.