20130319

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

Astronomy 210, spring semester 2013
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 how stars have to be hotter inside than on the outer layers in order to be stable interesting because I would assume it would have to be equal hotness rather than one part being hotter than the other."

"I like how stars are formed from dust clouds in space. I already knew this, I just imagined them forming one star at a time not in batches from 100 to 1,000."

"I found it interesting that stars aren't equally formed in their density, but do have a consistency of having a more dense center and not so dense outer layer, I found this interesting because I've never actually gave the density of stars much thought before."

"I found it interesting that you can tell the composition of a cloud based on it's color. For example, if you see a pink cloud in space, you know it is predominantly hydrogen."

"The white dwarfs have really compressed densities, and if you were to get a teaspoon of that material, on Earth, it would weigh about 15 tons. That's pretty hard to imagine."

"That two stars can have the same luminosity even if one is smaller than the other, it must burn hotter than the larger, though."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found the proton-proton chain a little confusing because I don't understand how you get deuterium."

"How come giant stars are much larger in diameter than the main sequence stars, but not much larger in mass? And how come they have low average densities?"

"Most of it."

"I had trouble understanding the 'house party' model. I understand the type of partiers but I am having a hard time relating it to stars."
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Because if the gas is cooler than 5 million K the hydrogen can't fuse because the protons don't collide violently enough to overcome the repulsion of their positive charge."

"'Cold fusion" is implausible because at low temperatures, hydrogen would be moving too slowly; therefore, the hydrogen wouldn't collide very much, if at all.
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I think you should have a more streamlined website, yours is looking a bit archaic." (It's called "old-school." No Java, no cookies, no log-ins, and it's simple enough to work in just about every browser on every device.)

"Would you volunteer to go to Mars? That would be one mind-blowing one-way trip." (Which is why Mrs. P-dog would not approve.)

"If you knew you would not burn to death would you personally fly an airplane through a low density star?" (Well, yes, but I can think of lots of other awesome things I could do if I knew I could not burn to death.)

"Favorite TV Show?" (Community. Pop pop!)

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