Astro 162 Planetary Astrophysics Problem Set 11
Due Thursday in class.
Readings: None.
Problem 1. Tearing Up the Oort Cloud
(a) Consider an invading star of mass M = 0.5M speeding through the Oort Cloud
at a velocity relative to the Sun of V = 30 km/ s. I

Astro 162 Planetary Astrophysics Problem Set 2
Due Thursday in class.
Readings: Landstreet, sections 4.44.6
Problem 1. Protostellar Disk Sizes and the Centrifugal Barrier
The gravitational collapse of a molecular cloud to form a star leads inevitably to t

Astro 162 Planetary Astrophysics Problem Set 5
Readings: Landstreet, Chapter 10, pages 265274, also page 290
Problem 1. Deep Impact
Estimate, to order-of-magnitude, the critical size of the meteor plunging into the Earths
atmosphere that would fail to be

A ONE-ZONE MODEL FOR SHELL FLASHES
We shall consider a model of a compact star, a white dwarf or a neutron star, accreting matter
at a constant rate Ma . We assume spherical symmetry, and we ignore all dynamical eects of
matter falling onto the surface. T

DYNAMICAL STABILITY OF SPHERICAL STARS
We consider rst a spherical star in a hydrostatic equilibrium. r0 , 0 , and P0 are the radius,
density, and pressure, assumed to be known function of the mass fraction, Mr , with 0 < Mr < M ,
where M is the total mas

12 December 2006 by JJG
Stellar Magnetohydrodynamics
Magnetohydrodynamics (MHD) is the generalization of hydrodynamics to electrically
conducting uids. Major astrophysical applications include stellar interiors, accretion disks,
and the interstellar mediu

SPHERICAL WINDS SPHERICAL ACCRETION
Spherical winds.
Many stars are known to loose mass. The solar wind carries away about 1014 M yr1 of very
hot plasma. This rate is insignicant. In fact, solar radiation carries away 4 1033 erg s 1 , which
reduces solar

WHITE DWARFS (DEGENERATE DWARFS)
White dwarfs are stars supported by pressure of degenerate electron gas, i.e. in their interiors
thermal energy kT is much smaller then Fermi energy EF . We shall derive the equations of structure of white dwarfs, sometime

Protostars and planets
For review articles on this large but still very much frontier subject, see [1].
A protostar can be dened as a star which, although of normal composition, does not yet burn
hydrogen; its luminosity is oset instead by gravitational c

Neutron stars and black holes
Like white dwarfs, neutron stars are strongly degenerate compact objects of roughly one solar
mass. But whereas white dwarfs are supported against gravity by the zero-point motion of electrons
(electron degeneracy pressure),