20180327

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

Astronomy 210, spring semester 2018
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.
"The H-R diagram. I think is really interesting you can get so much information from something so simple."

"The Coulomb barrier--I pictured trying to put two magnets together and pictured that little forcefield around them when you try to make them touch."

"The concept of fusion is definitely interesting, because fusion of hydrogen requires a temperature hotter than the core of the sun, yet fusion can happen because the immense pressure forces them together. Really cool."

"You can kind of tell what a nebula is made of by its color."

"NEBULAE! I always see these nail tutorials and they say, 'How to Make Your Nails Look Like Galaxies' but they should really be called 'How to Make Your Nails Look Like Nebulae.'"

"That stars can be born at the same time, but age differently. The house party model used to describe how stars become main sequence stars was helpful."

"That about 90% of an average star's life is spent on the main-sequence. I didn't really know how long the main-sequence portion of its life was."

"Star life cycles. Also, the house party model was very cool and actually pretty accurate and on point."

"The explanation of star cluster ages as a house party because it helped me see similarities and grasp the concept better."

"The house party model is actually hilarious and I love it."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"How there are stars that are both hotter or colder than the sun, while both being smaller or larger in size."

"The H-R diagram was a little hard to understand due to the placements of the variables but after some hard thinking I got it."

"Parts about cold and hot fusion, and I tried looking it up but there were really confusing explanations to go along with it."

"Fusion rates were kind of confusing for me. Also, the H-R diagram was difficult for me as well."

"How mass and temperature affects the rate of fusion confusing. I need some more explanations."

"The star cluster ages an were confusing until I read the house party model. Is it dumb if it works?"

"It all seemed pretty straightforward, honestly."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [94%]
Medium-mass (sunlike): medium luminosity [100%]
Low mass (red dwarf): dimmest luminosity [94%]

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 [100%]
Medium-mass (sunlike): medium fusion rate [100%]
Low mass (red dwarf): slowest fusion rate [100%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
 break heavy elements apart. *** [3] create convection currents. [0] overcome gravity. * [1] overcome repulsion. ************ [12] (Unsure/guessing/lost/help!) [0]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"The protons must be under pressure and in heat in order to produce energy, without the adequate heat the protons can't hit each other."

"Cold fusion would be implausible because hydrogen only gets squeezed a lot when under very high pressures and temperatures, which causes fusing and energy release. This couldn't happen without high temperatures."

"Hydrogen won't be moving fast enough and due to that they won't be colliding as much and less violently so they might not be able to overcome repulsion."

"Atoms need heat to be able to move fast."

"Um, I don't know--if it's cold, there's no friction, no friction equals no fusion? That's wrong, I know it is--I just don't want to re-read the presentation slide again."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [94%]
Reflection: blue [94%]
Dark: brown/black [100%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [94%]
Reflection: small dust particles [88%]
Dark: large dust particles [88%]

Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
Medium-mass (sunlike): medium main-sequence lifetime [100%]
Low mass (red dwarf): longest main-sequence lifetime [81%]

If there was an open invitation to a house party (no specific time given), when would you show up?
 Early, or on time. **** [4] When the most people should be there. ************ [12] After most everyone has left. [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"There was a lot of information in this section, so I'm not sure what I'd want to ask. I'll figure that out over spring break."

"Need more explanation on the birth of stars, please."

"Why are quiz and test questions worth 4 points?" (Partial credit on the multiple-choice questions are 0.5 points. If each question was one point, then the partial credit amount starts looking pretty small, even if it's still proportionally the same amount. Also, it makes adding up the total points for each exam (100 points) cleaner.)

"Are you a punctual person for parties?"

"Would you show up on time or fashionably late to a house party?" (I'm the one throwing the house party.)

"So, at my work 10 minutes early is 'on time,' anything after that is considered late, thoughts?" (Your workplace doesn't sound like much of a party to me.)