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

Astronomy 210, spring semester 2014
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.
"Hydrogen fusion always sounded like such a complex concept to me, but after reading it through it seems much more straight forward then I thought. I mean the idea that the sun creates helium from hydrogen is a little abstract still to me but I can't believe how much energy the sun has. It turns 4 million tons of mass into energy every second! No wonder stars implode."

"I found the nebulae fascinating. Just their mere aesthetics are very attractive and appealing. Such as the Horsehead Nebula shapes, its amazing how so coincidently a dark nebula looks like a common farm animal."

"I found reading about the different types of nebulae was really interesting and I thought some of the pictures in the presentation were beyond awesome."

"I thought the house party diagram was the most relatable and funny example, but actually made sense :)"

It's crazy to me the way star formation works- that hydrogen in clouds forms new stars and dust becomes planets around the stars. It just seems like so much is created from something so simple!"

I found it interesting that there are only blue, pink, and black in the different clouds in outer space. I found this interesting because because I would not have thought that those colors would exist in outer space."

I thought the house party metaphor for star cluster ages was really interesting and made it a lot easier for me to understand and remember the different ages and what they mean. I also thought the nebulas were interesting especially how what different ones are made of correspond to what color they are. I am looking forward to learning more about them."

"I liked the cheerleading analogies because I used to cheer and it helped the concept of fusion make more sense to me."

"I found the H-R diagram very interesting. The diagram was interesting to me due to how many patterns of stars it contains on one single diagram yet is fairly easy to read."

"I thought the slide on hydrogen fusion was interesting, especially because the example you used with cheerleaders. I used to be a cheerleader in high-school so it was easy for me to understand the idea that layers are an important factor in more massive star cores."

"I really liked reading about the different nebula. My roommate has a book called The Stargazers Handbook and the front is covered with nebula and stars. I always was curious what made those colors, and it's interesting that interstellar reddening is the same reason that the sun produces such amazing colors at sunset."

"Something I found interesting from the presentation previews was the cheerleader examples of high mass and high pressure, also fusion and luminosity. This was personally interesting for me because it makes me understand it in a better way."

"I found it very interesting how our star formation happens. How the shock waves are a very dominate trigger for the star formation, also how a collapsing cloud of gas does not form a single star. That instead they form into fragments producing thousands of stars, how a stable group of stars are formed called star clusters."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The principle of hydrostatic equilibrium confuses me. Do all stars have the same amount of layers? And are all the layers the same size, because the amount of pressure becomes more as the layers get closer to the center then does that mean the the size of the layer increases, not in weight but in thickness (area)?"

"I was a little confused on the fusion part just because it didn't all make sense to me when I was reading it."

"Just comprehending the size of nebula and how long they take to develop is hard to imagine. One year is nothing in the universe but so much seems to happen in it for a human."

"I was mostly confused about the fusion segment of the presentation. It makes sense in theory to me that high temperature equals more fusion but I am still confused about it because it's so science-y. I'm immediately thrown off when words like 'hydrogen' and 'proton' come in to play. I still don't feel confident about what a proton is."

"Nothing was too confusing, I just need to look over the presentations more."

"I'm confused on how to find the star's fusion rate."

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  *** [3]
create convection currents.  *** [3]
overcome gravity.  [0]
overcome repulsion.  ***************************** [29]
(Unsure/guessing/lost/help!)  * [1]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"If the temperature and pressure is too low the hydrogen won't get squeezed enough and won't collide with one another."

"The protons in the nuclei are positively charged and repel each other. The temperature in a 'cold fusion' is too cool and slows the speed of the nuclei and doesn't allow for the protons to overcome their repulsion and collide."

"Because they are not moving as fast."

"I have no idea."

Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Low mass (red dwarf): slowest fusion rate [97%]
Medium-mass (sunlike): medium fusion rate [100%]
Massive: fastest fusion rate [97%]

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [94%]
Reflection: blue [92%]
Dark: brown/black [97%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [94%]
Reflection: small dust particles [92%]
Dark: large dust particles [94%]

If there was an open invitation to a house party (no specific time given), when would you show up?
Early, or on time.  ** [2]
When the most people should be there.  ********************************* [33]
After most everyone has left.  * [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"So when is the house party?"

"I love the little jokes you put into the presentations it makes them so much more fun to read/study."

"The pictures of nebulae are beautiful."

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