Online reading assignment: the Milky Way (NC campus)

Astronomy 210, fall semester 2014
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on the Milky Way's shape, size and composition and spiral arm structure and formation.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"Dark matter, since we don't know much about it."

"PimpStar Rims, and how they work just like the stars in a spiral galaxy do."

"The process in which astronomers discovered the galaxy--that we didn't know what the Milky Way was until the 20th century, and it's crazy that we can look out the band of stars across the night sky to realize our galaxy is disc-shaped."

"That the name of the Milky Way actually came from it appearing to look like 'milk.' It looks more like dirty water to me."

"Globular clusters are cool because they can show us where we are in our galaxy."

"The PimpStar Rims and the MonkeyElectric lights, as they create whole images and not just rapidly-moving lines. This was very interesting as it did not occur to me this was a product you could buy, or even was a product."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The only thing I found somewhat confusing from the presentation was the process by which a larger galaxy could essentially swallow a neighboring dwarf galaxy causing the larger galaxy to produce density waves and create arms to the galaxy, giving it a spiral look and flattened disk. This was confusing to me as it was skimmed over and not covered well in the presentation."

"Nothing too confusing."

"The element building cycle."

"What a spur is."

"How PimpStar Rims work."

In your experience, how much of the "Milky Way" (the band of faint stars across the celestial sphere) have you been able to see in the night sky?
As much as can be seen with the naked eye.  ****** [6]
Not very much.  ******** [8]
Barely seen it.  * [1]
(Never been able to see it.)  ** [2]
(Unsure/guessing/lost/help!)  [0]

Using the most powerful light-gathering telescopes in the darkest skies, up to how much of the stars in our entire galaxy can be observed from Earth?
1%.  * [1]
5%.  ** [2]
10%.  ***** [5]
50%.  **** [4]
100%.  * [1]
(Unsure/guessing/lost/help!)  **** [4]

If you did not have access to a mirror while camping, what could you do to find out whether or not you're having a bad hair day?
"I usually always have my phone on me, so I would use my camera on my phone or the reflection of the screen when its black."

"Find a riverbank and look at your basic self in the reflection. #nofilter"

"Everyday is a bad hair day for me."

"Just brush it back or put it in a bun."

"Ask one of my honest friends."

"Feel my hair."

"Inspect your shadow to see if there are any crazy stray hairs coming off your head."

Look at PimpStar Rims (*.html) for cars, or MonkeyLectric Rims (*.html) for bikes. Briefly explain how they work.
"Rapidly blinking lights can be coordinated to create patterns when swept across our field of view."

"The MonkeyLectric rims for bike happens by the light being smeared out with the movement of the tire."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Have you seen Interstellar yet and if so did it mess you up?" (Not yet--did it mess you up?)

"If we can only ever see a small part of the entire Milky Way, how do we know how many stars are in it?" (There are many different pieces of evidence that help us answer that question. Evidence that you will be tested on.)

"Dark matter--it doesn't make sense. How can it not be seen?" (But all the stars in the Milky Way feel its gravitational influence.)

"You are correct in saying the PimpStar Rims look terrible."

"Do you ever get questions about your bike lights? (Like, just now.)

"Are there only certain stars that make up our spiral arms? I know that hot, blue stars were mentioned, but are these the only ones that make up spiral arms?" (There are all types of stars that are born in a spiral arm density wave--massive, medium-mass, and low-mass stars--but the massive stars are the brightest and shortest-lived, so they "blink off" just after leaving the spiral arms, while rest of the dimmer, longer-lived medium-mass and low-mass stars continue on, unseen but always present.)

"High density waves that cause star formation as clouds of gas collide with them. If I understand correctly, then, the waves are moving significantly slower than the clouds of gas. If that's right, what is the medium of the high density waves and why does that trigger star formation?" (Think of the "traffic jam" analogy--the cars drive down a road, but crowd together and move slower when traffic gets backed-up, before spacing out and speeding up again. The location of the traffic jam remains constant as the cars pass through it. So, cars = gas and dust, and traffic jam = density wave location, where gas and dust slow down, compress, and trigger fresh star formation.)

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