Online reading assignment: fusion, nebulae, star cluster ages (SLO campus)

Astronomy 210, spring semester 2015
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 fusion, nebulae, and star cluster ages.

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.
"I found the colors of the nebulae interesting because I never though about there only being specific colors that we can see with the naked eye in space."

"I found it interesting that the cheerleader model was used for this fusion explanation. I found this interesting because I would have never put the two together but when you explained it, it made sense."

"I liked the cheerleader references since I have been one all my life. So that helped me understand star mass/luminosity pretty well."

"Definitely how long a star lives because a young star is millions of years old which is just crazy."

"I found the relation of a star's mass, pressure, luminosity and fusion rates to be interesting how they are intertwined."

"Supernovas and nebulae are awesome! who doesn't look at a nebula and go 'wow that's radical!' "If they don't they're probably a sociopath. That's how you do psychology 'astronomy style.'"

"The nebulae--the active diagrams helped understanding to correspond with the actual picture of what was seen by the observer."

"Unfortunately I didn't find anything interesting this week, but I never really do when ready the books. I most like it when we go over in class, you make things more interesting and easier to understand."

"I like the analogy about going deeper in a swimming pool and how you feel the pressure."

"I find it interesting that the energy comes from hydrogen smashed together to make helium."

How the different layers of the sun create pressure in the middle so that fusion can happen."

"I actually never knew that stars can die out."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The emission/reflection/dark nebulae and how to differentiate between them."

"I actually did not have too much trouble with this passage to be honest."

"Turn-off points did not make sense to me."

"How to determine a star cluster's age using the H-R diagram..."

"Why does temperature make it so the hydrogen can fuse?"

"The stars are just really complicated sometimes."

"I find pretty much all of this confusing but I know I'll understand when you explain it in class."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [100%]
Medium-mass (sunlike): medium luminosity [100%]
Low mass (red dwarf): dimmest luminosity [100%]

Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Massive: fastest fusion rate [82%]
Medium-mass (sunlike): medium fusion rate [100%]
Low mass (red dwarf): slowest fusion rate [82%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  ** [2]
create convection currents.  **** [4]
overcome gravity.  *** [3]
overcome repulsion.  *********************** [23]
(Unsure/guessing/lost/help!)  ** [2]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"There needs to be a lot of pressure and energy in order for fusion to take place."

"Protons don't warm up fast enought to be able to bump into each other."

"Because the atoms would not be moving fast enough to break the Coulomb barrier; no energy would be created."

"This is because a hydrogen nucleus is just a proton and protons always repel each other because they are both positive. Under low pressure/temperature they won't get enough pressure so they will move too slowly to overcome the repulsion."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [74%]
Reflection: blue [79%]
Dark: brown/black [97%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [88%]
Reflection: small dust particles [76%]
Dark: large dust particles [85%]

Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
Massive: shortest main-sequence lifetime [68%]
Medium-mass (sunlike): medium main-sequence lifetime [100%]
Low mass (red dwarf): longest main-sequence lifetime [68%]

If there was an open invitation to a house party (no specific time given), when would you show up?
Early, or on time.  ***** [5]
When the most people should be there.  ************************* [25]
After most everyone has left.  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I thought space was zero gravity, so how do stars have weight and collapse on themselves?" (Their mass creates gravity that pulls them in on themselves. Like Earth's mass does to itself, and to you and me.)

"I wonder what you would say if you ever saw one of your formers students in the television. Would you say, 'oh that used to be my student,' or would you just nod?" (Well, in the latter case, I wouldn't just nod, I would #facepalm.)

"What time would you show up to the house party?" (I'm always late, but worth the wait.)

"I'd tell you a chemistry joke but I know I wouldn't get a reaction." (...)

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