Astronomy 16 – Astrophysics: Stars, ISM, and Galaxies

Archive of Assignments

Week 13

posted 12/11

Take a look at the slides from our final class [pdf].

posted 12/10

Homework #10 [pdf] is due on Friday, December 14 by 6pm. There are three problems on it.

posted 12/7

The assignment for class 26 [pdf]: our last class meeting. We'll discuss the distance ladder and the evidence for the expansion of the universe and the big bang.

Hubble Deep Field

Take a look at the slides from Thursday's class [pdf], with images of other galaxies, interacting galaxies, galaxy clusters with gravitational lensing...

posted 12/4

Tonight's lab number 5 [pdf] involves making color-magnitude diagrams of two star clusters.

The assignment for class 25 [pdf] on Thursday takes us beyond the Milky Way, and has you reading selectively in Ch. 20. As part of your preparation for the class, look over the slides we looked at in Tuesday's class [pdf].

posted 12/3

Homework #9 [pdf] is due on Sunday, December 9 by 9pm. We'll have our regular SA session on Thursday night but also (likely) one on Sunday afternoon from 3 to 5 pm.

posted 11/30

The assignment for class 24 [pdf] on Tuesday focuses on the Milky Way, and has you reading selectively in Ch. 19.

Study this good sketch of the Milky Way. And marvel at this photo montage of the Milky Way.

Sparke and Gallagher Milky Way

Week 12

posted 11/23

The assignment for class 22 [pdf] on Tuesday after Thanksgiving break continues our study of white dwarfs (Ch. 18, sec. 1) and then moves on to the fates of more massive stars (supernova explosions – see image below – neutron stars and black holes). As part of the assignment, you should answer the last two questions on this worksheet [pdf] and email me your responses by midnight on Monday.

Crab Nebula HST

For your reference, here is the eclipsing binary lab manual [pdf] from last Tuesday night's lab meeting.

Read these guidelines for the midterm [pdf] which will be in class on Thursday. The key thing to note is that you are to prepare a set of hand-written notes which you'll be able to use when you take the exam.

Week 11

posted 11/17

The assignment for class 21 [pdf] on Tuesday focuses on degeneracy pressure both in the context of post-main-sequence stellar evolution (Ch. 17, sec. 2) and white dwarfs (Ch. 18, sec. 1). As part of the assignment, you should answer the first three questions on this worksheet [pdf] and email me your responses by midnight on Monday. You can also take a look at these few images [pdf] that summarize a few aspects of ISM, star formation, and stellar evolution.

proplyds in Orion

This week is short – Thanksgiving is happening at the end of it.

Week 10

posted 11/14

The assignment for class 20 [pdf] on Thursday asks you to review the material from the first two sections of Ch. 17 and finish the Jeans Mass derivation we started at the end of class on Tuesday.

posted 11/10

The assignment for class 19 [pdf] on Tuesday focuses on star formation in the ISM and post-main-sequence evolution.

Abell 39

posted 11/5

Homework #8 [pdf] is due on Monday, November 12 by noon. We'll have our regular SA session on Thursday night but also one on Sunday afternoon from 3 to 5 pm.

Week 9

posted 11/6

The assignment for class 18 [pdf] on Thursday does not involve any new reading. But the assignment document does have a few specific, new things for you to think about as you contemplate 21 cm emission, H II regions, and thermal balance in the ISM.

posted 11/5

Homework #8 [pdf] is due on Monday, November 12 by noon. We'll have our regular SA session on Thursday night but also one on Sunday afternoon from 3 to 5 pm.

posted 11/4

The assignment for class 17 [pdf] on Tuesday is all about the interstellar medium. To supplement the reading in Ch. 16, read these notes [pdf], print them out and bring them to class. These are identical to the notes posted last week. Note that I've asked you to bring with you answers to a couple of questions about dust extinction and reddening, relevant to a homework problem. You'll hand in your definition of color excess, E(B-V), at the start of class and then we'll discuss how the color excess of a star can be used to determine the amount of dust between us and the star and also correct our estimate of the star's distance for the effects of dust.

You should also look over the images of interstellar gas and dust shown in last Thursday's class [pdf].

Tarantula Nebula

Week 8

posted 10/30

The assignment for class 16 [pdf] on Thursday is the first of two about the interstellar medium. To supplement the reading in Ch. 16, read these notes [pdf], print them out and bring them to class

posted 10/29

Homework #7 [pdf] is due on Friday by 10pm.

posted 10/26

The assignment for class 15 [pdf] is simply more focus on the stellar structure material in Ch. 15, with an emphasis on nuclear reactions.

Week 7

posted 10/23

The assignment for class 14 [pdf] covers the rest of stellar structure: energy transport and energy generation. There's a lot of material – my assignment document has more detail than usual; please read it carefully and use it as a study guide. I am planning on reserving next Tuesday's class – possibly even all of it – to continue the discussion of this material.

posted 10/19

The assignment for class 13 [pdf] hydrostatic equilibrium – pressure-gravity balance, which we consider first in an atmosphere like the Earth's and then more generally throughout the entirety of a star (or gas giant planet).

Homework #6 [pdf] is due on Sunday by 7pm. Update (10/26): Now due at 9pm on Sunday (and there's an extra SA session from 3 to 5 pm on Sunday).

Week 6

posted 10/9

The assignment for class 12 [pdf] focuses on stellar spectral classification and the HR diagram. It includes some of Ch. 14 and also these supplementary slides [pdf].

You can look over the slides showing binary star spectra [pdf] that we looked at in class on Tuesday. And the radial velocity orbit simulator plus this eclipsing binary simulator, which we did not actually look at in class.

posted 10/6

Homework #5 [pdf] is due on Friday by 7pm.


The assignment for class 11 [pdf] focuses on binary stars and stellar masses (including trends that we find regarding the distribution of stellar masses and their correlation with other properties of stars).

Week 5

posted 10/1

We will have our first midterm on Tuesday night at 8pm in SC 158. It will be a completely open-book exam (students can use their notes, too).

posted 9/27

The assignment for classes 9 and 10 [pdf] focuses on measuring and characterizing the properties of stars. Note that it's a combined assignment for both days next week. There's a problem to hand in at the beginning of class on Thursday.

Week 4

From Thursday's class: color image of Barnard 68 and six-wavelength image montage of the same cloud.

Barnard 68

posted 9/25

The assignment for class 8 [pdf] wraps up radiation and matter. No new reading, but review.
You can look over the images and problem solution from class:

solar spectrum

And the graphical solar spectrum as well as my solution to the spectral line depth and optical depth problem. And the periodic table as well as hand X-rays both negative and positive.

posted 9/24

The fourth homework [pdf] is available and due on Sunday evening. I hope to grade it and return it to you by the end of the next day so you can look it over prior to Tuesday night's exam.

Read over the short lab manual for lab 2 [pdf] before coming to lab on Tuesday night. You will also be relying heavily on two tutorials for using AIJ to reduce [pdf] and analyze [pdf] your data. Download them, too, though you don't have to read them in detail ahead of time.

posted 9/23

Read this short bit of background information on the Ring Nebula and download this complete, raw dataset of Ring Nebula observations [zip] that you'll be using in this week's lab. Unpack the zip file, open up AIJ, and load one image from the main folder. Prof. Cohen will have office hours on Monday from 3:30 to 5:00 and Tuesday from 12:45 to 2:00 during which time you're urged to come by with your computer and practice a little with AIJ. The manual for the lab will be posted here by Monday evening.

The assignment for class 7 [pdf] focuses on radiation transport and local thermodynamic equilibrium.

Week 3

posted 9/18

The assignment for class 6 [pdf] covers the same material – the first four sections of Ch. 5.

You can look over the slides shown at the beginning of class 5 [pdf] as well as my solution to the in-class problem [pdf]. Oh, and my solution to the challenge problem on the back [pdf] (that we didn't discuss in class).

NGC 2442

posted 9/17

The third homework [pdf] is available and due on Sunday afternoon.

posted 9/16

The assignment for class 5 [pdf] covers the first four sections of Ch. 5.

Week 2

posted 9/14

Spectra of blackbodies of various temperatures. Taken from the Openstax Astronomy textbook.

posted 9/11

The assignment for class 4 [pdf] covers quite a few more aspects of light. We'll start by going over the problems I gave out [pdf] at the end of class on Tuesday. Bring your solutions to class, and then move on to the new material in the class 4 assignment.

posted 9/10

Please read the manual/information for our first lab [pdf] prior to coming to lab. There is also a document containing supplemental information [pdf], that's referred to in the main document that has things like step-by-step instructions for using the AstroImageJ software. There is also an article about digital images and color astronomical images [pdf] that you should read before coming to lab. If you plan to use your own computer to work with telescope data in this class this semester, then in addition to doing this reading, you should install AstroImageJ (see link on the right side of this page, you'll have to look for the download link once you're there) on your computer and download the zip file containing the Ring Nebula data you'll be using the lab.

The second homework [pdf] is available and due again on Saturday afternoon.

posted 9/9

The assignment for class 3 [pdf] covers parallax (distance measurements of stars) and the inverse square law of light (can also be used to estimate distances, or for stars of known distance, it allows us to determine their radiant power output, or luminosity).

Week 1

posted 9/5

The first homework [pdf] is available and due on Saturday afternoon.

posted 9/4

The assignment for class 2 [pdf] covers orbits. It invites you to play with the gravity simulator on the right side of the main page. Can you build a circular orbit?

Also, take a look at my solution to the problem you solved in class [pdf], if you want to check over your work. And look over the slides I showed in class [pdf]. The SOHO website has some amazing images and nearly real-time images of what the Sun looks like right now.

Sun Halpha

posted 9/2

The main thing to read and think about prior to our first class meeting on Tuesday is this document, what I call the assignment for class 1 [pdf]. It does contain some very modest reading and video viewing that you should do and think about, but you should think of the assignment document itself as the main resource and guide for what we'll be doing in class on Tuesday. Usually these class assignments will include some textbook reading. This first one though includes some scanned pages from a different textbook, two written proofs, and a video. To make it easier for you, I've collected and linked those items here: Bennet pp. 90-92, 98 [pdf], first approximate derivation of the expression for centripetal acceleration, second derivation, and the video about angle, size, and distance.

posted 7/9

Look over these images and movies of last summer's solar eclipse and think about this: When we say the Moon and Sun appear to be the same size, what is it, exactly, that's the same about their sizes? Certainly not their diameters or radii in meters.

nashville eclipse montage
credit: Richard Sparkman

The next eclipse visible in the US will be on April 8, 2024. The path of totality goes from Texas to Maine.


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Last modified: December 16, 2018