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 find it interesting how many stars are out there and how they work. I don't understand how everything works, but it's great to know that there are people that care and share their learning with us to help us understand."
"I thought it was interesting about the weight of the layers in the sun being related to water in a swimming pool because that example helped me understand it."
"The cheerleader example for pressure and mass really helped."
"How you used cheerleaders as a representation for how more or less pressure on the core of a star produces more or less fusion and thus is brighter, or dimmer."
"The section on the star mass and luminosity relationship, because different types of stars have different relationships between mass, density, and luminosity."
"How there are only three true nebulae colors meaning there are a lot of fake pictures of space."
"I really liked reading about nebulae. I never knew there were more than one type, and apparently there are three."
"It was really cool to learn the reasons behind certain colors of nebulae. I didn't know that emission gave off a pinkish color, or that reflection was blue, but the example about cigarette smoke sometimes taking on the blue tint made sense."
"Learning more about how a star forms was quite interesting. They are such massive objects, its fascinating seeing how they started."
"Supernova shockwaves seem like an interesting subject to look into further."
"Pictures of cheerleaders. Just kidding. I really like the house party model, it's a great way to remember this! It was one of the easiest to remember models so far in class."
"I found your house party diagram very helpful in describing the different types of stars, it helps me visualize the subject better."
"Having been to lots of house parties I found the house party model to be the most interesting."
"I thought the house party analogy was very funny but also a good technique to help us remember information on the stars."
"I actually thought the house party model was helpful :P at first I was like how can this even relate to astronomy but then reading on I was like 'ohhhh.' Also, I was on Xbox as I was reading that and it just made the whole thing relatable."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The H-R diagram is kinda confusing to me."
"I found the H-R diagram to be confusing to me because I'm not sure how to use it."
"I'd like a deeper explanation of fusion, it's a lot."
"Fusion was actually really confusing for me. I don't really understand it, I think the book just confused me when I tried to read it."
"I was very confused about the proton-proton chain and CNO cycles."
"Hydrostatic equilibrium was a confusing concept, just because it seemed pretty complicated, but I feel like I can understand it if I just study the GIF animation a bit more."
"Fusion rates."
"Why are the masses all over the place for the non-main sequence stars?"
"Whether a nebula emits light itself, or is it reflecting light."
Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [90%]
Medium-mass (sunlike): medium luminosity [97%]
Low mass (red dwarf): dimmest luminosity [90%]
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 [77%]
Medium-mass (sunlike): medium fusion rate [93%]
Low mass (red dwarf): slowest fusion rate [80%]
Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart. ***** [5] create convection currents. ***** [5] overcome gravity. *** [3] overcome repulsion. ************* [13] (Unsure/guessing/lost/help!) **** [4]
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Because the hydrogen nuclei are both positive so they naturally repel each other. So they need to be hot to move fast such that they overcome their repulsion. The atomic nuclei have to come at each other with enough speed and temperature to break the repulsion. An object's temperature is just a measure of the overage speed with which its particles move. A high temperature ensures that collisions, between nuclei are violent and a high density ensures that there are enough collisions, to produce enough energy to keep the sun stable. Cold fusion is implausible because there needs to be heat in order to be collisions. "
Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [90%]
Reflection: blue [87%]
Dark: brown/black [90%]
Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [83%]
Reflection: small dust particles [83%]
Dark: large dust particles [83%]
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 [90%]
Medium-mass (sunlike): medium main-sequence lifetime [93%]
Low mass (red dwarf): longest main-sequence lifetime [83%]
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. ************************ [24] After most everyone has left. [0]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Would it be possible to go over fusion in class? I don't really understand it."
"The textbook states that 'true stars' are powered by nuclear fusion. Is there such a thing as a 'false star?' the stars we see at night or is it a sun-like star but powered by something else?" (A "star" in general denotes something that emits light from its own energy source. The main-sequence stars (what we could consider as "true stars") fuse hydrogen in their cores to produce energy. Protostars aren't hot enough to fuse hydrogen, but they produce energy from their own gravitational contraction. Supergiants and giants produce energy from fusing stuff heavier than hydrogen.)
"I'd like a fair amount of lecture on these topics."
"Did you come up with the house party analogy yourself?" (Actually, yes.)
"The house party model was totally relatable. Thanks for that."
"What's the craziest party story you have from when you went to college?" (I don't really remember specific details. So maybe it really was a crazy party. #coolstorybro)
"What happens when a star explodes?" (We'll find out in next week's class.)
"With all the squeezing that takes place from a sun collapsing into black holes, and the pressure there being so immense, could there possibly be a new form of fusion taking place past the event horizon?" (Well, no one will every know what goes on within the event horizon.)
"If hydrogen is just one proton and no neutrons, but all protons 'hate each other,' how the heck can a molecular cloud be filled with proton-rich hydrogen, yet still 'self-start' by continually clumping together exponentially until it somehow pulls in even more stuff to create more complex structures? It just seems kinda contradictory." (Don't underestimate the power of the gravitational force. If a molecular cloud is cool enough that stuff moves slowly, and if it is large enough (light years across), then over time gravitational forces between everything will eventually pull the cloud in on itself to make a star (or planets).)
"Do you speak other languages?" (Is Hawaiian pidgin a language?)
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