ASTR0 81 - Assignment #8
1. The Chandrasekhar mass is the maximum mass which can be supported by fully
relativistic degenerate electrons. We can derive an approximate value for this as follows:
Start with the equation for the pressure of a relativistic de

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ASTR0 81 - Assignment #3
due Friday of week 3 before noon
1. Calculate the theoretical diffraction-limited resolution of a 10m telescope at wavelengths of 300 nm (UV) and 1 m (IR). Under what circumstances might each be
realized in practice?
2. The diffra

ASTR0 81 - Assignment #4
due Friday of Week #5 before noon
1. The apparent magnitude of the Sun is -26.8.
(a) How much brighter does the Sun appear that the brightest star, which has m =
-1?
(b) What is the distance modulus of the Sun?
(c) What is the Sun

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ASTRO 81 - Assignment #7 Solutions
1. (a) Estimate the pressure at the center of the Earth. Assume Hydrostatic Equilibrium
(H.E.) - i.e. gravity pulling inward is balanced by pressure pushing outward.
Equation of H.E.
GMr
dP
=
dr
r2
Continuity Equation

ASTRO 81 - Assignment #8 Solutions
1. Chandrasekhar mass problem
On page 239, pressure of relativistic electron gas
1/3
Pdeg,rel
1 3
=
8
N
hc
V
4/3
e
N
= 0.12hc
V
4/3
On page 233, we have the electron number density
N
V
=
e m H
e
e = 2 for a carbon whit

Mid-Term No. 1 for Astro-81
Prof. Ghez
Closed notes, closed book, and no calculators are allowed
SHOW YOUR WORK FOR PARTIAL CREDIT - BE SURE TO
ATTEMPT ALL PARTS OF PROBLEM EVEN IF YOU DONT KNOW
HOW TO DO THE EARLIER PARTS
Name:
Student ID Number:
Here ar

Reading Assignment #6 - Blackbodies
Were going to cover Chapter 5 in a slightly different order than the book presents
the material. You dont really need any of the material from the first part of the
chapter t

_
ASTRO 81 Assignment #5
due Frtday of Week #6 before noon
_
To get full credit for these problems you need to show all your work. Longer problems with
more sub-parts are worth more points.
1. Order of magnitude: On a smoggy day in the Bay Area, one can j

Key Concepts from Last Lecture:
Spectral Line Formation:
The proportion of electrons in an excited energy level is given by
the Boltzmann equation:
Ni
gi E/kT
N
0 =
g
0 e
(g = 2n2)
The proportion of atoms of a giv

Key Concepts from Last Lecture:
1. Calculate the wavelength or frequency of a line associated with a
transition between two energy levels: | E1 E2 | = hn
2. Bohr Model of Hydrogen Atoms quantized energy levels
En = - 13.6 ev / n2
3. Name Energy Transi

Key Concepts from Last Lecture:
Telescopes:
Image size (on detector) = focal length x angular size
Atmospheric seeing can limit angular resolution, if atmospheric
coherence length (r0) is smaller than telescope diameter
r0 = 10 cm (l / 500 nm)1.2
if r

Key Concepts from Last Lecture:
Electromagnetic Radiation can be described in terms of
Luminosity L Energy/time [W]
Flux Density Energy/time/area [W/m2]
Intensity
Energy/time/area/solid angle
(solid angle [steradian] = Area / r 2 )
Intensity
I = Fs /
Tot

Key Concepts from Last Lecture:
Plotting luminosity vs. temperature (or absolute mag. vs color) creates
a Hertzsprung-Russell (HR) diagram.
Main Sequence (class V) [stars in equilibrium; H to He]
Spectroscopic Parallax with main sequence stars
90% of

Key Concepts from Last Lecture:
1. Explain and calculate effects of dust
1. Effect on DM:
m M = 5 log dpc -5 + A
2. Color Excess (reddening): E(B-V) = (mB mV) (MB MV)
Av / E(B-V) = 3
3. On Flux: F = F e-
optical depth; d = x dr; opacity = n(num

Key Concepts from Last Lecture:
How can we describe the locations of objects in the sky?
Horizontal coordinate system:
altitude (a), azimuth (A) relative to observer on Earth
[zenith, horizon, meridian]
Equatorial coordinate system:
right ascension (R

Key Concepts from Last Lecture:
Astrophysics is an experimental and theoretical endeavor to
understand physical processes throughout the universe.
Electromagnetic radiation is the most commonly used carrier
of information in astronomy, but isnt the on

ASTRO 81 Assignment #5
due Friday of Week #6 before noon
1. If a slab of glass 0.2 m thick absorbs 50% of the light passing through it, how thick must
a slab of identical glass be in order to absorb 99.9% of the light?
2. Order of magnitude: On a smoggy d

Key Concepts from Last Lecture:
1. Bolometric magnitudes (apparent & absololute)
2. Magnitude 0 is often defined by the bright star Vega
3 (or BB)
2h
1
The radiation of many objects can beBapproximated
as an ideal
(T ) =
2
h/kT 1
c
e
black body ,

MidTerm No. 1 for Astro81
Prof. Ghez
Closed notes, closed book, and no calculators are allowed
Answers need only be given to 1 signicant gure for full credit
SHOW YOUR WORK FOR PARTIAL CREDIT - BE SURE TO
ATTEMPT ALL PARTS OF PROBLEM EVEN IF YOU DONT KNOW

ASTRO 81 Assignment #8
due Friday of Week #10 before noon
1. The Chandrasekhar mass is the maximum mass which can be supported by fully
relativistic degenerate electrons. We can derive an approximate value for this as follows:
Start with the equation for

Reading Assignment #12 Stellar Interiors (part 1)
Read Karttunen section 10.1 (4 pages)
Now that weve learned how to measure a stars external properties (such as
temperature, luminosity, mass, and radius), we