(1) Please hand this problem in on a separate sheet so Prof Morrison can grade it.
Using
ADS http://adsabs.harvard.edu/abstract_service.html)
and/or the astronomy library, find the oldest article you can written
in an astronomical journal, or the oldest book (or chapter in a book)
(preferably written for a non-general audience) which discusses a
theory for the formation of the solar system, or of the Earth/giant
planets/asteroids/comets in the context of solar system
formation.
The articles or books should be pre-1960 at least. You
may talk with each other about your searches, but each student should
hand in a discussion of a different book or article. (Email me to check you have chosen a suitable article. You should choose your article by Thursday August 30 at the latest, as I will be out of town from Fri 31 to Wed 5. IF YOU DO NOT EMAIL ME WITH A SUGGESTED ARTICLE YOU WILL RECEIVE NO CREDIT FOR THIS QUESTION. ) Include a copy
of the article or chapter with your handed-in work. (Apart from the
Kant/Laplace theories from the 18th century, I have found interesting
articles as early as 1905 in the astronomical literature.) I'll give a
prize for the most interesting paper.
(a) Describe the theory that is put forward in the article or book
in 2-3 paragraphs. Your target audience should be other physics and
astronomy students at your level. NB: Clearly describe the
physics that is used in this theory.
(b) Contrast this theory with currently popular theories on your chosen topic.
If we have not discussed this yet in class, come talk to me or email
me.
(c) Discuss the evidence that is used to bolster the
theory, and any problematic facts mentioned by the author. Remember
that confronting the theory and the evidence is at the heart of
science. More than half the marks for this question will be given to this section.
(d) Is the theory still a viable one, in the light of new evidence that
has come to light in the last 50 or more years?
In total, you should write about 2-3 typed pages.
(2) In class, we saw that the rate of growth of a planet can be written as
where M is the mass, t is time, ρ and ρs are the densities of the solid planet and the planetesimal swarm, G is the gravitational constant, R is the planet radius and v is the relative velocity.
a) Using the relationship between mass and density for a solid body and the chain rule, rewrite the above equation in terms of dR/dt.
b) Explain in words what style of accretion is represented by each of
the two terms in the brackets, what controls which style of accretion
dominates at a particular time, and how the density of the planetismal
swarm and the relative velocities of the objects affect the growth of the planet.
(3) Using the plots in notes which show (a) the temperature variation in models of the planetary disk (use the solid lines) and (b) the equilibrium condensation temperatures for atomic elements and selected molecules, along with the diagram of solar system abundances which is also in class notes (to work out the most common atoms and molecules in the protoplanetary cloud), calculate the range of likely locations of the ice line in the Solar System as it formed. Compare this with the position of the planets today.