Physics & Astronomy 590
Spring 2023 Homepage
Univ. Louisville
Instructor: Dr.
Gerard Williger, NS 206, tel 852-0821
e-mail: gmwill06@*
where *= louisville.edu (please do not e-mail to my Groupwise acct)
My homepage is here
Office hours:
by appointment;
*I will not entertain questions on problem sets on the day they are
due*
Lectures: Tue/Thu
11am-12:15pm, Nat Sci 313
Text: Foundations of Astrophysics,
Ryden & Peterson, 1st ed., Addison-Wesley (2010)
The course objective is to learn basic the basic physics of
astronomical phenomena. A mastery of calculus
and introductory (calculus-based) college physics is assumed, plus
the material for Astronomy 307.
Differential equations will help, but if you
have not had them, you can pick up what you will need. The
lectures will begin on Tuesday, Jan. 11.
A password-enabled protected
site will contain answers to homework and midterm problems, if
I do not
pass them out in class. I may also put commentaries on common
homework errors there as well.
Finally, all the PowerPoint files for a recent Astro 107 class, plus
animation files,
are on the protected site. They're an excellent overview for
the material in this course, and I
highly recommend your looking at the files. We'll try to cover
roughly chapters 13-24 in our textbook.
GRAPHING CALCULATORS ARE BANNED ON TESTS.
UL
Student Support Page for the COVID-19
situation.
Here are
links for supplemental material and additional explanations
astro-news
for Astro 107 (see for solar plasma ejection article etc.)
Reading/Schedule:
10-12 Jan: Chap 13; + Astro-107 Ch11 slides
17-19 Jan: Chap 13-14
24-26 Jan: Chap 14-15 + Astro-107 Ch12 slides (MQ1, Jan 26)
31 Jan-02 Feb: Chap15
07-09 Feb: Chap 15-16 (Quiz 1, Feb 9)
14-16 Feb: Chap 16-17
21-23 Feb: Chap 17-18 + Astro-107 Ch13-14 slides (Board Pblm 1, MR,
Feb 23)
28 Feb-02 Mar: Chap 18 + MIDTERM
07-09 Mar: Chap 18-19 + Astro-107 Ch15 slides
14-16 Mar: SPRING BREAK
21-23 Mar: Chap 20 + Astro-107 Ch16-17 slides
28-30 Mar: Chap 20-21 (Board Pblm 2, Mar 30, JG)
04-06 Apr: Chap 22 (Quiz 2, Apr 6); ; guest lecture Brad Peterson
11-13 Apr: Chap 23 + Astro-107 Ch18 slides (Board Pblm 3, Apr 13,
SB)
18-20 Apr: Chap 24 + Astro-107 Ch19 slides
Tue 25 Apr, 11am, NS 313: review session
Fri 28 Apr 11:30-2:00pm: Cumulative FINAL EXAM
Presentations should be about 10 minutes talking, 2 minutes of
questions each, unless class agrees to longer
TIME/PLACE FOR PRESENTATIONS: Tue 2 May at 11:30am, NS 312. Talks
will be in person.
CHAPTER TOPICS:
13 - magnitudes, stellar luminosities/sizes, binaries, radial
velocity/light curves
14 - stellar atmospheres, Hertzsprung-Russell diagram
15 - stellar interiors, equations of stellar structure
16 - interstellar medium, H II regions
17 - star formation, evolution of solar mass stars, Cepheids/RR
Lyrae stars
18 - white dwarfs, neutron stars, stellar mass black holes,
supernova remnants
19 - Galactic morphology, structure, rotation curve, nucleus
20 - galaxy classification, spectra, supermassive black holes,
Hubble-Lemaître law
21 - active galaxies, accretion disks, quasars, intergalactic medium
22 - galaxy clusters/superclusters, galaxy mergers
23 - cosmology (Newtonian and Einsteinian), spacetime metrics,
Friedmann equation
24 - accelerating Universe, cosmic microwave background, Big Bang,
consensus model
CHALLENGE PROBLEMS: Done for learning. The ~60-70 problems total to
1% of the grade. Learn them for tests.
COUNTS PROBLEMS -- TO BE TURNED IN: These are graded homework.
You can work together, but must turn in your
own, original solutions.
YOU
MUST SHOW YOUR WORK (INCLUDING ORIGINS OF ALL NUMBERS)
SO THAT I CAN
FOLLOW YOUR CALCULATIONS AND GIVE PARTIAL CREDIT.
PLEASE STAPLE ANY WRITTEN HOMEWORK! LOOSE PAGES MAY BE LOST.
HOMEWORK
ASSIGNMENTS
Challenge problems are for
practice and will be similar to some test problems. They are
for learning/exercises, and to be turned in for
participation credit. Ask for help if you need it to learn
how to do them.
CHALLENGE PROBLEMS
HW01, due Tue 17 Jan: 13.1, 13.2, 13.3, 13.4,
13.5, 13.6 (use material from 307 or ask if you need help)
HW02, due Tue 24 Jan: 13.7, 13.8, 13.9, 14.2 (use Ch 5 info),
14.5, 14.7 (hint: use bolometric magnitudes)
HW03, due Tue 31 Jan: 14.1, 14.3, 15.3, 15.5, 15.7, 15.8
HW04, due Tue 07 Feb: 15.4, 15.6, 15.9, 16.4, 16.7 (F0 star
problem), 16.10
HW05, due Tue 14 Feb: 15.1, 16.2, 16.6, 16.8, 16.9, 17.5 (just
calculate the max time the sun could shine at its current luminosity
and starting at its current radius by contraction, similar to
previous problems)
HW06, due Tue 21 Feb: 16.3, 17.1, 17.3, 17.4, 17.6, 18.1
HW07, due Tue 28 Feb: 15.2 (calculate explicitly), 16.1, 17.2,
18.3, 18.7, 18.8 (for reference, the shortest known pulsar periods
are 1 millisec),
HW08, due Tue 21 Mar: 18.2, 18.4, 18.5, 18.6, 19.1, 19.2,
19.5, 19.6, 19.9, 19.10
HW09, due Tue 28 Mar: 19.3, 19.4, 19.7, 19.8, 20.4, 20.7
HW10, due Tue 04 Apr: 20.1, 20.2, 20.3 (use the
Hubble-Lemaitre law), 20.6, 21.1, 21.2
HW11, due Tue 11 Apr: 21.3, 21.6, 21.7, 21.9, 22.1 (Virgo
Cluster has d=16 Mpc, diameter of Local Group is 2 Mpc), 22.6 (use
the star counts material from Ch. 19)
HW12, due Tue 18 Apr: 22.3, 22.4, 22.5, 23.2, 23.3, 23.4
HW13, due by 5pm Mon 24 Apr: 23.1, 24.1, 24.3, 24.5 (put in my
mailbox or e-mail)
COUNTS PROBLEMS/EXTRA CREDIT
Any paper
or seminar/talk write-ups should be typed, on paper. Please use TWELVE POINT
TYPE (not smaller).
Grammar/spelling/style count. CITE any outside sources you
use (papers, websites etc.)
Reading beyond the textbook and notes is encouraged! It's
good to learn how to look up information.
Keep a backup for yourself. Do about 300 words (1
page) unless otherwise noted. Definitions do NOT count
against the word total.
IN GENERAL for paper
summaries,
0) Look up and list any definitions you need to learn. If
you need help, ask.
i) your first sentence should be a punchy summary: "This
paper shows/discusses ..."
Then clearly identify at least these points:
ii) the main science question(s) or paper goal(s) in the
context of a brief background description e.g. "why is this
investigation being done"
iii) data source description (e.g. telescopes, surveys etc.
if it is an observational paper) or whether the paper is
theoretical; not needed for a review paper
iv) methods and error analysis (unless it's a review paper)
v) results, discussion/conclusions
vi) future work/implications
vii) whenever possible, be quantitative and specific, rather
than general and/or vague
viii) at the beginning of the paper, emphasize in one
sentence what is NEW and DIFFERENT in this paper compared to
other work in the field
IMPORTANT: Avoid copying phrases or sentences verbatim. Put
the material into your own words. Use plural with "data",
and singular with "datum". Do not use constructions like
"The article says", but rather give the author's last name
(if a single author paper), the two authors' surnames (if a
two author paper) or the first author's last name + "et al."
for >=3 authors.
COUNTS 1: Summarize Bessell 2005, ARAA, 43, 293,
"Standard Photometric Systems", on the class protected site
(Articles subdirectory).
It's long so I just want
parts of it: Beginning/Sec 1-2.3, 5.1-5.3, 6-8. (By the way,
Robert F. Wing was my teacher for the equivalent of Astro
308.)
This paper is long, so for this summary write a maximum of
about 500-600 words (2 pages).
The goal is to learn about the various filter systems, so give
details about each for the given sections and compare them.
Note that it is a data/tools paper, so it does not have the
traditional science question, data,
methods sections etc. Just summarize it and cover the main
points. NB: broadband has width dlambda > 400-1000 A, not
< 1000 A.
It's a misprint in the paper. See broadband filter widths in
Table 1.
Due Tue 24 Jan, 2023 at the beginning of class.
COUNTS 2:
Color Problem:
(a) Compute the Planck function in
wavelength for 4400A, 5500A, 6200A, 7700A for temperatures 3000K,
5000K, 10000K, 20000K. Also make a plot for Vega (T=9600K).
Plot your data points from 500-22000A, showing a continuous
curve for each temperature.
The wavelengths correspond to the centroids of the B,V,R,I filters
respectively, and
the temperatures correspond roughly to M, G, A and B stars.
List in a table the fluxes for each temperature-wavelength
combination.
Using the Planck curves as fluxes (dlambda=1A is fine),
compute and list in a table the colors in terms of magnitude B-V and
R-I vs. temperature.
(You can plot them as well, but you must give a table.)
SHOW A SAMPLE CALCULATION FROM START TO FINISH WITH NUMERICAL STEPS
INCLUDED
SO I CAN FOLLOW IT. Explain how you got your results.
Do NOT give code. (It's too hard to read, you may use a
language I do not use and it's not generally what one gives in a
paper.)
Rather, describe your calculation with equations and plug in numbers
for one example.
Remember that Vega defines all magnitudes and colors as zero.
(b) Why do astronomers tend to use B-V as a main reference for
colors of spectral types rather than R-I?
Due 9 Feb (extended by 2 days), at the beginning of class.
COUNTS-3: Stellar Spectral Classification Problem:
Identify the spectral
classes and subclasses for the spectra e-mailed out on Feb. 10
(and given on paper on Feb. 14).
1) Due on 23 Feb (extended by 2 days) at
the beginning of class
2) Identify the stars by spectral class and
subclass. Do not spend much time to determine the luminosity
class (I-V), as that is more difficult.
(Most are V, though not all. You can try if you like,
based on line widths, though it is not required.)
3) Give all the identifying reasons you can (all spectral
indicators covered in class or wherever else you can find them).
Explain your reasoning fully.
Include a labelled version of the spectrum, identifying as many
lines as you can.
Note which sorts of lines go together based on the figures in
the lecture notes.
4) Give sources for any material you use beyond the book or
lecture.
5) Remember that you only have the optical portion of the
spectra.
6) Give
justification for your classifications, in terms of narrow
lines, broad lines, flux peak, slope, "raggedness" (in
reality weak lines), continuum flux at 3200-3500A relative
to peak flux or any other features you see. ANNOTATE each
spectrum with line identifications to be clear.
See a sample, annotated ground-based solar spectrum (with
telluric (Earth's atmosphere) plus Fraunhofer names for
lines) here
Common lines (in Angstroms) are:
TiO bands in the red (sometimes very broad), including 4584,
4626, 4761, 4810, 4847, 4954, 6650-6850 (v broad),
7050-7150, 8432, 8683A
H-alpha 6563
NaI doublet at 5896 (may not be resolved)
HeI 5876
HeII 5411
FeI 5270 (solar spectrum)
H-beta 4863
C2 4670 (broad, shallow; see Swan Bands)
HeI 4471
H-gamma 4342
CaI & FeI (blend), 4308 /4309 (Fraunhofer "G" lines,
strong in sun=G2V star)
CaI 4226
H-delta 4103
FeI 4045
CaII H,K doublet lines at 3935,3970
H-epsilon 3970 (calculate higher order lines yourself or
look them up, as needed - they sometimes are visible)
HeI 3965
FeI 3820 (Fraunhofer "L" line, strong in Sun=G2V star)
MgI 3835
FeI 3730
Balmer break 3646
You can find more information at http://skyserver.sdss.org/dr1/en/proj/advanced/spectraltypes/lines.asp#spectab
You can find a GREAT online tool via the WKU
Astro 106 online spectral calculator
Another resource: Columbia
U solar spectral exercise (includes description of A-K
lines from 19th century)
Also, see the paper by Kesseli et al. (2017, ApJS, 230, 16)
on the class protected site under "Articles" or on ADS.
You are free to look up any other stellar spectral
catalogue, list of lines etc.
CITE YOUR REFERENCES.
COUNTS-4: Color-magnitude
Diagram Problem. This is worth 2% on the grade.
Go to the class protected site and look in the Counts4
subdirectory. Download two files:
File-1: tab_cl01_index_bvri.xlsx - a table of apparent (not
absolute!) BVRI magnitudes for a star cluster
File-2: pecaut13apjs208.9_bvri_tab5_mainseqcolors_excel.xlsx - a
table of main sequence colors and temperatures from Pecaut &
Mamajek (2013),
ApJ Supp, 208, 9
In addition to these use Table A.5 in Ryden & Peterson, which
has a list of absolute V-magnitudes for main sequence stars, though
in a less detailed grid (but sufficient for our purposes).
1) Due on Tue Mar 7 at the beginning of class
2) Plot up color-magnitude (C-M) diagrams for the stars in
File-1. Caution: not all stars are detected in all
bands.
Non-detections are indicated by the "flag" value of 99.999. Do
not consider those magnitudes.
Use V as the reference magnitude. Try these colors: B-V, V-R, R-I,
V-I
Label your C-M diagrams and axes clearly.
Remember that many stars (about 30-40%!) have no B magnitudes,
because they are below the magnitude limit of the observations.
Some also have no I magnitudes, though the fraction is small.
So, there will be significantly fewer stars in B-V (x-axis) vs V
(y-axis) compared to other C-M diagrams.
Plot from hot to cool as left to right on the x-axis, and
faint to bright as low to high on the y-axis. This mimics the
H-R diagram.
If you need help with plotting, ask your classmates. If they
cannot help, then ask the instructor.
3) Compare the various colors for the C-M diagrams. Which
one(s) are most useful to determine the main sequence turn-off and
why?
4a) Assume no reddening. Which spectral type and effective
temperature T_eff are best indicative of the main sequence
turn-off?
Do they vary depending on the color you
pick? What is the corresponding or equivalent B-V color of
your turn-off and its uncertainty?
What is your uncertainty in spectral type and
T_eff? (We use (B-V) as a reference color, but note that it
may not be the best color to determine
the main-sequence turn-off.)
4b) Now assume a color excess of E(B-V)=0.25. What is the
corresponding main sequence turn-off and
spectral type and T_eff? How does the effect of adding
a color excess compare to the equivalent (B-V) uncertainty in (4a)?
5) For the main sequence turn-offs and uncertainties in 4a-b, look
up and list the corresponding absolute magnitudes M_V in Table A.5.
Interpolate as necessary.
6a) Assume no reddening. What is the distance to the
cluster in pc and uncertainty?
6b) Now assume 0.25 mag of E(B-V). Calculate the extinction
A_V (using the empirical value for R) and use it with a distance
estimate. Now what is the distance to the cluster in pc?
7) Again consider your main sequence turnoff spectral type and
T_eff, with and without a color excess.
Consult the mass-age-main sequence lifetime table from the Australia
Telescope National Facility site.
Logarithmically interpolate to get the age associated with your
T_eff for your main sequence turn-off,
since the mass-age relation is a piecewise power law. How old
is the cluster in Gyr without reddening? with reddening?
What is your uncertainty without reddening? with reddening?
What are your overall conclusions about the age of the cluster and
the presence of any reddening?
Ask for help from the instructor if you need it. Ask questions
if something is ambiguous or confusing.
COUNTS 5: Summarize Neelamkodan et al. (2021),
"ALMA Reveals a Cloud-Cloud Collision", on the class protected
site (Articles subdirectory).
Note that it is an observational paper, so it does have the
traditional science question, data, methods sections etc.
This is a regular "letter" or short article, so keep a summary
to 300-400 words, minus definitions and references..
Due Tue 21 Mar, 2023 at the beginning of class.
COUNTS 6: Summarize Arentsen et al. (2019), "The Pristine Inner
Galaxy Survey (PIGS) I: tracing the kinematics of metal-poor
stars in the Galactic bulge", on the class protected site
(Articles subdirectory).
Note that it is an observational paper, so it does have the
traditional science question, data, methods sections etc.
This is a regular "letter" or short article, so keep a summary
to 300-400 words, minus definitions and references.
Due Tue 4 Apr, 2023 at the beginning of class.
COUNTS
7: Summarize Davis et al. (2015), "A Fundamental Plane of
Spiral Structure in Disk Galaxies", ApJL, 802, L13, on the class
protected site (Articles subdirectory).
Note that it is an observational paper, so it does have the
traditional science question, data, methods sections etc.
This is a regular "letter" or short article, so keep a summary
to 300-400 words, minus definitions and references.
Due Tue 17 Apr, 2023 at the beginning of class.
EXTRA CREDIT:
1) TBA
PRESENTATIONS:
Here are the rules.
0) Pick a paper you can understand *backward and forward*. If
there are terms, concepts, parameters etc. you do not understand,
I expect you to learn and explain them to the rest of the class (and
to me), in your write-up, slides and presentation.
If there are too many such terms/concepts/parameters for you to do
this, do not pick such a paper. It's MUCH better to do a
*great* job
on a simple paper than a so-so job (at best) on an extremely
complicated one.
1) topics+proposed papers due Thu 10 Mar (before Spring Break)
2) maximum 10 minutes+2 minutes questions, strictly enforced, SLIDES
DUE (POWERPOINT OR PDF) TBA
3) I recommend about 7-10 slides
4) explain a-the scientific question, b-background, c-the
methods/data, d-what is new (the discovery/result), e-the meaning
for the big picture/science and future work
5) Your audience is your classmates. They should understand what you
do. If they don't, you haven't done your job to explain it to them.
6) You're encouraged to get graphics from other articles, Wikipedia
etc. BUT CITE your sources!
7) FORBIDDEN topics: General relativity, anything related to GR
(such as complex calculations with neutron stars or black holes),
"strange" stars or other quantum mechanics not covered in class, or
any other subject which is not covered in our textbook. GR is
not a prerequisite
for our class, and most people have not (yet) taken it, though I
recommend it for future studies.
8) Use a REFEREED journal article, 4-6 pages maximum, on any subject
in Astro 307 or 590. The more recent the article is, the better. Try
to stay with one published in the last 5-6 years, to keep technology
and science current for the class. You are encouraged to read other
papers for background material, and these can be longer, but your
primary one should be short. Review papers on anything (as they tend
to be long and not have a science question), general relativity,
modified gravity, quantum gravity and nuclear physics we haven't
covered (e.g. quarks) in particular are NOT allowed. The
standard journal search engine is
ADS.
I will introduce its use to you if you need it.
8) There is a STRICT upper size limit of 6 pages (4-5 pages
preferred) in any journal. No exceptions. Remember, these talks are
SHORT.
9) I recommend getting an article from the following. Try especially
the Letters from each journal.
Nature
Astrophysical Journal
Astrophysical Journal
Letters
Monthly Notices of the
Royal Astronomical Society
Monthly Notices of the
Royal Astronomical Society - Letters
Astronomical Journal
Astronomy & Astrophysics
(especially Letters)
Publications of
the Astronomical Society of the Pacific
Icarus (solar
system journal)
Publications of the Astronomical
Society of Japan
If you wish to present a paper summary from another journal, please
clear it in advance with G. Williger.
Other refereed journals are available via the NASA ADS
site, and
arXiv preprint server (look for PASJ
articles or other hard to find articles here) site.
10) WRITEUP:
You will also need to write an approximately 600 word/two
page summary of your paper, which is worth 1/3 of the
presentation grade (more than a regular paper summary):
a) science question
b) observations/data sample (if observational) or methods
(if theoretical)
c) results
d) conclusions
e) further work
This is due typed, on paper, when you make your
presentation. You may include background material from
other papers.
Cite liberally.
GOOD PRACTICE FOR SLIDES:
Use variable colors, font size, boldface, underlining,
italics etc. Avoid monotony. **MAKE FONT SIZE BIG for those
in the back of the room.
No more than 1 slide per minute.
Each slide should have a title of one to a few words - keep
reminding the audience what's going on and guide step by
step.
Use background boxes, indentations, bullets etc. Avoid
unbroken blocks of text.
Use "telegraph language", minimizing words. Do not write
many complete sentences. Speak them instead.
Have at least one graphic per slide, even a small one.
A little humor can be helpful, but keep it restrained so it
does not dominate your message; use like salt and pepper in
a recipe.
Put references on the slides where they are used (just
author and year). Do not make a slide for references.
Your LAST slide should be "conclusions and further work". It
will start the discussion after your talk.
**Anticipate one to a few questions and have slides as
"extra material" in case you need them.
WHEN TALKING:
Do not read your slides.
Modulate your voice pitch and speed. Speak with expression.
Do not be monotone. Do not speak too fast.
*MAKE EYE CONTACT WITH YOUR AUDIENCE FREQUENTLY.*
Avoid saying "um". It distracts your audience from your
message.
*PRACTICE* your talk so it's smooth. Have your
friends/classmates critique you.
Know your material very well and anticipate some potential
questions. Have a slide or two ready after the end of your
talk
in case someone asks the question you think will come under
"Extra Material".
Keep to your time limit (~10 minutes). You should practice
your talk at least 3 times with it successfully within your
time limit.
Ideally, you should not need notes. But, use them if you
must.
Participation grades are subjective and are subject
to change. They result from
a combination of class participation (comments and
questions) plus performance at any problems done at the board in
class, or assisting other
students doing so. If you never say anything or skip class (which I can note in any way,
including not picking
up homework) then you can get as little as zero. I also am
less
likely to be generous with
participation if you habitually don't
turn in any written, assigned
homework, since doing homework generates questions
and feedback on common
misconceptions.
GRADING:
Grades are composed of
tests 80%: 1 cumulative final, 1 midterm, 2-4 quizzes; also 0-9
miniquizzes (1% each), possibly questions at the board
presentation 7%
homework + participation 13%
Details are on the syllabus.
The presentation will involve summarizing a paper from the
literature.
Partial
Credit:
Homework and tests will have
partial credit available. You MUST show
your work, in particular the
equations which are used to begin a
calculation, to get any credit at
all. You must keep track of significant
digits. If the least
accurate number going into a calculation has n
significant digits, then the
answer should have that number, also.
If you happen to do the wrong
homework problem instead of an assigned
one, you will typically not get
credit for it. Leaving a question
blank definitely earns a zero.
On homework, I also count it as a sign of lack of
participation.
Scientists
need
to check their own work. To this end,
you are expected to have an
idea what a reasonable answer is, even though
you might not get the
correct answer.
A
reasonable answer has the correct units -- use dimensional analysis!
It also has an order of
magnitude
which is not wildly
inconsistent with information given in the problem or common
knowledge. For
example, calculating a core temperature of the Sun to
be 3K is a nonsense
(unreasonable) answer, because its surface and even
Earth are much hotter than
that. If your answer is way off
and you
note it and attempt to explain where the problem might be,
I will take it into
consideration.
If
you give a nonsense answer due to simple arithmetic or
mathematical
errors and do not catch it,
you may not get partial credit for setting up the
problem correctly.
Here are also links (from
an Astronomy 107 links site) for recent
discoveries,
(simple) equations
used in that class
and supplemental
material.
Planned material to cover (subject to
modification; links for supplemental material are
provided):
orbital mechanics, Earth-Moon system, tides, nature of
light, telescopes/detectors, our solar system and others
We will begin stellar astrophysics if time permits.
Topics
covered:
stars, stellar structure,
interstellar medium, star formation, the Milky Way,
galaxies, cosmology
Additional
material from other chapters and books will be added as
needed.
If you miss a test and you give
me a week's
advance notice with a
documentable reason, the make-up may be an
oral exam. Missed quizzes
may be excused, with documentation, with their weight put on
the midterm or final exam.
General test policy is that
once you leave the room, you can't come back in.
You are permitted to help
each other in groups, but you must turn in your own work.
Grading will be done on a
curve.
There is no fixed
percentile for grades, nor any absolute standard for letter
grades. The plus-minus
grading system (A, A-, B+ etc.) will be used.