Mean molecular weight
Assume gas is composed by neutral atoms, ions, electrons with charge neutrality satisfied.
We would like to calculate the mean weight per particle in units of mu
Ions: denote with i each nuclear isotopic species.
Zi nuclear char
Astro 465 Assignment 2
Due: 10 am Oct 3, 2016, in CCIS 2-107 or CCIS 4-285
(10pt) 2.1 Consider the constant density model:
(a) (7pt) Show how the virial theorem works for this constant density sphere, if we had to chosen to consider only
the part of the s
Astro 465: Stellar Astrophysics II
"I conceive that the chief aim of the physicist in discussing a theoretical problem is to
obtain insight - to see which of the numerous factors are particularly concerned in any
effect and how
The dynamical timescale dyn
We see on HRD that some stages of stellar evolution are very fast (like RG stage), so may
be there HE is not applicable? Lets assume that a start is not in HE. How fast then do
changes to the structure of a star occur?
The gravitational field
) gravity is the driving force behind stellar evolution.
In the general, non-spherical case, the gravitational potential is the solution of the Poisson equation
r2 ' = 4G
Another form (integral represen
Stellar dimensionless analysis
Homology, OR Homologous stars.
Consider a sequence of simple spherical stellar models in complete equilbrium where
one model is related to any of the others by a simple change in scale. Assume that the
models all have t
The virial theorem
The virial theorem is the most important consequence of selfgravitating bodies in hydrostatic equilibrium. The virial theorem connects two important energy reservoirs of a star
the gravitational potential energy of the star and sta
Solutions to HW 2
2.1 (constant density model)
(a) Consider equation for the potential energy, but integrate it only to radius r:
3 GM 2 5
The total kinetic energy is
3 dm = 12
For a constant
ASTRO 120 Lecture 24
Which of the following is not a possible consequence
of increased cloud cover?
A. Increased reectivity lowers the surface temperature
of the Earth.
B. Increases the greenhouse effect because water
vapour is a
Geology of the
The maria on the moon have few craters
compared to the mountainous regions. What is
the most likely process at work?
A. The early lunar atmosphere smoothed out the
B. The mountainous regio
ASTRO 120 Lecture 23
The layer of gas surrounding a planet.
The gravity holds gas close to surface
The pressure* of the gases balance gravity
Atmosphere is mostly in equilibrium
(weather is the reason its only mostly)
How to Build a Solar System, Part 1
Astronomy 120 Lecture 17
Based on all the
characteristics in the table,
the planet should be
Semi-major axis (AU)
Geology of the Big Terrestrials
Astronomy 120 Lecture 22
Why do the continents remain on the surface of the
Earth for long (Gyr) periods of time?
A. Being rocky, they stay in one place.
B. The terrestrial magnetic eld keeps them at the
C. The oce
ASTR 120 Lecture 15
True or False: The Hubble Space telescope (2m
aperture) can resolve the disk of Pluto (1200 km)
at a distance of 40 A.U. in red light (= 600 nm).
C. Not enough information given
1 A.U. = 1.51011 m
(Geologically) Dead Planets
Astronomy 120 Lecture 21
Planets differentiate (separate into layers) for the
same reason that:
A. Mentos explode in Diet Coke
B. Your voice sounds squeaky when you inhale
C. Your hair stands up when you get a static ele
The Grand Tour
Astronomy 120 Lecture 18
What is the resolution of the VLA at 20-cm. The dishes
are 25-m across and the separation between the dishes is
diraction limit (arcsec) = 2.5 10
Interferometry all the
Astro 120 Lecture 14 Alice Koning (firstname.lastname@example.org)
Dene magnication, light-collecting area, and
Contrast the various types of ground-based optical
Explain why radio telescopes need to be larger
Dating (no, not that kind of dating) and Space Travel
Astronomy 120 Lecture 19
The Lull before The Storm
Methods: Radioisotope Dating
Positive protons repel each other. Bound by strong
nuclear force (scales like number of part
How to Build a Planet
Astronomy 120 Lecture 20
The composition of the primordial solar nebula is
thought to be very similar to the current composition
The core of the Sun
The outer layers of the Sun
The atmosphere of Venus
The surface of
Light and Matter ASTR 120 Lecture 13
KNOW YOUR TERMS
Dissociation Molecules splitting up into
Ionization Atoms splitting up into ions (atomic
nuclei) and electrons.
Ionization produces plasmas, which are gases of free
ions and ele
ASTR 120 Lecture 12
Why we care about light
Colour, frequency and wavelength
Atoms (unlikely today)
If I observe a First Quarter moon at midnight, how
long until the next high tide?
If this is the moon phase tonight,
what will it look like in one week?
Torques from other planets in
the solar system causes
In a gravitational eld, a
spinning top will precess.
Orbits and Tides
ASTR 120 Lecture 11
On a typical coastline, how many high tides are there
E. Get ya booty on the oor
Bound orbits balance the
kinetic energy of the
object against the
energy of the
Astronomy of the Solar System
Fall 2015 Erik Rosolowsky
Answering why is colonizing the
solar system so hard?
(in 5 easy steps)
i. Understanding the skies from Earth.
ii. How we came to fathom the deepness of the
iii. The Laws of the Uni
The Land of Physics
Astronomy 120 Lecture 10
Which of the following will be true if you were
standing on the moon?
A. Your weight would be the same as on Earth, but your
mass would be different.
B. Your mass and weight would be the same as on
Astronomy 120 Lecture 7
Who invented the telescope?
B. Tycho Brahe
E. Some Dutch Fella
After the Greek Philosophy
Greek and Roman civilizations waned into
Medieval Europe (Library of Alexandria
Gravity is a Harsh Mistress
ASTR 120 Lecture 10
Conservation and Energy
The Universal Law of Gravitation
Gravitation and Kepler
Centre of Mass
Conservation. Physics Style
Conservation refers to one of these vocabulary
concepts (angular mome
Lecture 8 SCIENCE! (Nature of)
Galileo was able to observe a complete set of
phases for Venus much like those of the moon (new,
crescent etc.). Which phase of Venus should appear
the largest to us on Earth?
A. Crescent Venus
B. A half-illuminate
How do you write the number 0.0254 in
Quick Scientic Notation Recap
A number between
1.0 and 9.999.
A power of ten
100=1 103 = 1
The Oldest Science
Astronomy 120 Lecture 6
If I went out at 6:00 a.m. and I saw the moon high
overhead to the South (on the meridian), what phase
would it be?
A. Waxing Crescent
B. Waxing Gibbous
C. Full moon
D. Waning Crescent
E. Last Quarter