Please pick up your midterm from your TA during
your lab.
Any re-grade questions, please email me.
*What are Jovian planets made of?
*Jupiter & Saturn: almost all H & He, very little metal &
rock (less dense)
*Uranus & Neptune: <50% H & He, the rest hydro
Assignment #7 due on Tuesday
(tomorrow) at 10pm.
If youre planning on working on extra
credit assignments, dont wait til week 10!
Todays lecture:
How massive stars evolve
How massive stars die
Neutron stars
Black holes
Gravity (relativity)
What about h
Please pick up your midterm from your TA during
your lab.
Let me know if you have any questions.
The Solar System is 4.6 billion years old. How do we know
this?
You can find the oldest rock on Earth. But how do we know
how old that rock is?
Atoms are i
Assignment #10 due on 6/7.
Final Exam on Monday 6/8 8am
Review session:
Friday 6/5, 2:15-3:15pm.
Royce 190
Study guide for the final exam: check
your email.
Office hours this week:
Wednesday 1:30-2:30pm
Friday 11-11:30am
Cosmic Microwave Backgrou
Assignment #7 due on Tuesday (5/19) at
10pm.
If youre planning on working on extra
credit assignments, dont wait til week 10!
Todays office hour changed to 1-2pm.
Your overall midterm score =
(Midterm 1 / 48 + Midterm 2 / 50)*100
Composition: Classification of Stars
The spectra of
stars were first
classified during
the late 1800s.
Stars with the
strongest
hydrogen lines
were labelled
A, stars with
somewhat
weaker
hydrogen lines
were labelled B
stars, and
Composition:
Spectral
T
Please pick up your midterm from your TA during your lab.
Any re-grade questions, please email me.
Homework #5 due on Tuesday at 10pm.
Ive added links to latest astronomy news (under Week 5
for this week). Ill keep adding them whenever I see
something new
> B: H
0> H: B D 5:
H M
: >:
:D
:
M#
:
M : H : #
> : A H: H=>
:
: >D A H: H=>
:
Measuring Stars
5= H E DE: H>: D H
:
A:
DB D : > H=:> A> =H
> =H :
-> H
:
:BE: H :
DBED >H>D
> H=: EE : H => H > ED >H>D D
:
M D ?: H
> H
D
D
BD : > H H D ?: H
1
AA
A:
:
*Assignment #4:
*Due on Tuesday 4/28 10pm
*Four processes have shaped the terrestrial
worlds:
*Impact cratering
*Tectonism
*Volcanism
*Erosion
Core: highest-density material; primarily
metals such as nickel and iron
Mantle: rocky material of moderate dens
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 ,
/ .
,K) 9% 1 9H7
0 0\
w y 9 \W
7) \"7
A!) \O 4
Astronomy 115 \I 6 6 12 March 2010
b/A /
Final Examo\o
\0
\x
l. A cup of espresso sits neglected on a table in the Kerchkoff coffeehouse. Originally
boiling hot, it cools slowly to room temperature, at 20C. I
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
Astronomy 115, Winter 2017
HA 1
Due in lecture Friday, January 20th
1. Calculate the average molecular weight, M , of air. The mass composition of dry air
at sea level pressure of 1 atm and temperature of 25 C is 78% Nitrogen, 21% Oxygen,
and 1% Argon.
2.
Astronomy 115, Winter 2017
HA 2
Due in lecture Friday, January 27th
1. Although Hydrogen is a diatomic gas at room temperature (T = 300 K) and atmospheric pressure, hydrogen molecules dissociate into atoms at temperature above
3000 K. At temperatures high
Astronomy 115, Winter 2017
HA 3
Due in lecture Friday, February 3rd
1. Consider a system of N
stars and star clusters.
1 non-relativistic particles held together by gravity, such as
(a) Assume that all particles have identical mass, m, and derive the viri
Astronomy 115, Winter 2017
HA 5
Due in lecture Monday, February 20th
1. Consider two groups of students, A and B, each consisting of 10 students sharing a
total of 20c/ in 1c/ coins. Assume that the total number of coins is xed and all students can random
Astronomy 115, Winter 2017
HA 4
Due in lecture Wednesday, February 15th
1. Consider a grand potential d (T; V; ) = d (U
TS
N) =
SdT
(a) Write thermodynamic identities and Maxwell relations for
P dV
Nd .
.
(b) Show that, for a system in thermal and diusive
_
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
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