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

Astronomy 210, spring semester 2017
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.
"How 2.2 lbs of matter completely converted to energy produces enough energy to power Philadelphia for a year. Damn boi."

"Something I found interesting and super-fascinating as always is how absolutely stunning stars are. They are so beautiful--I don't think the night sky gets enough credit!"

"Hydrostatic equilibrium--I just had never thought about the layers of the sun, let alone layers of any object really applying pressure to the layer directly beneath it."

"I thought the comparison of our sun to cheerleaders was interesting and helpful because the example made it much easier to understand."

"The way nebulae have different colors and compositions I found really interesting. It makes me realize how little most of the population knows about the universe beyond earth."

"I really liked the explanation of the house party; it helped that section make a little better sense. And the pictures were funny! I also found the different colors of nebulae really cool!"

"The house party model, because it makes complete sense on how the stars age and behave."

"I found the representation of the house partiers for the star cluster age actually really helpful!"

"I found your house party model to be interesting, it was very amusing. I also was very intrigued by the process of the star formation, the supernova shock wave is very wind-blowing and amazing how it sort of jump-starts the formation of the star."

"I expected everything to be backwards like week, but I was pleasetly surprised everything made logical sense."

"I'm lost."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Still confusing to me is how blue and white both are hotter than red. It just seems so backwards!"

"Comparing luminosities and fusion lifetimes."

"The concept of fusion and exactly what it has to 'overcome.'"

"I didn't really understand how the proton-proton chain worked."

"I have absolutely no idea what is going on with the interstellar medium."

"The difference between reflection and emission nebulae is confusing because I'm still unclear about how the different colors come about."

"I was a little confused on how we tell a star cluster's age."

"I am still really confused about this house party scenario! I can't wait to get it!"

"Everything seemed pretty straightforward."

"Not sure yet."

"So very lost."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [87%]
Medium-mass (sunlike): medium luminosity [92%]
Low mass (red dwarf): dimmest luminosity [89%]

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 [87%]
Medium-mass (sunlike): medium fusion rate [95%]
Low mass (red dwarf): slowest fusion rate [87%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  ***** [5]
create convection currents.  *** [3]
overcome gravity.  ****** [6]
overcome repulsion.  *************** [15]
(Unsure/guessing/lost/help!)  ********* [9]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Cold fusion wouldn't work because nuclear fusion only occurs when the nuclei of two atoms get very close to each other. These violent collisions only occur when hydrogen gas is very hot, like at the core of stars."

"Fusion requires sufficiently higher temperatures and pressures to take place. Room temperature would not do anything."

"At cooler temperatures, particles move more slowly. Slow protons will repel each other because of their positive charges."

"They have to be hot to move fast or aggressive enough to overcome their mutual repulsion."

"Hydrogen has a positive charge so it repels each other and cold temperatures won't allow to move fast enough to collide with each other."

"The pressure that occurs in stars can't be replicated (yet)."

"It is only a hypothesis, it naturally happens within stars at millions of degrees so cold fusion isn't plausible at cold or room temperature."

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

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [95%]
Reflection: small dust particles [89%]
Dark: large dust particles [89%]

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 [71%]
Medium-mass (sunlike): medium main-sequence lifetime [89%]
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.  ****** [6]
When the most people should be there.  ******************************* [31]
After most everyone has left.  * [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Will you throw a house party? (ಠ_ಠ)

"The house party question threw me off because it made me pick between always wanting to be early/on time and not wanting to be bored because everyone else came later. In the end I listened to my anxiety ¯\_(ツ)_/¯"

"I'm now referring to my party guests as low-mass stars, medium-mass stars, and massive stars."

"What time would you show up at a house party?" (Mrs. P-dog and I are always just a little fashionably late. But you would never know when we leave, if we do an Irish goodbye.)

"Will we get more practice with the H-R diagram and how to find out how close/far the stars are from the sun?" (Let's see how well you do on Quiz 5; and we'll have a review session for these topics before the next midterm.)

"Will there be a study guide for second midterm?" (Yes. But survive Quiz 6 first.)

"No comment." (You just did.)

"I found brown dwarfs a little confusing. Are they still gaseous and just don't have any nuclear fusion happening or are they solid mass?" (They're gaseous, just not large enough to have enough gravity to squeeze their cores to fuse hydrogen. So they didn't make the minimum mass/gravity/core squeezing requirement to be a star (generating energy from hydrogen fusion).)

"How is it possible to measure a star's energy output?" (From measuring the star's luminosity--the amount of energy produced by fusion in its core each second must be equal to the amount of energy it gives off in the form of light at its surface.)

"I wish we could do these online reading assignments up until the day of class." (But I need the day of class to read everyone's responses and decide what specific topics to cover in class.)

"Answering this question isn't part of the grade on the online assignment, is it? (It's optional compared to the other questions, I mean.)" (Yes, this last section is optional. However, if you leave a lot of the sections above blank, then you can make up for that by leaving something substantial here.)

"What are your plans for spring break, P-dog?" (Going camping with Mrs. P-dog and Slumberjack, the Sleeping Forester. #optoutside)

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