## 20160329

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

Astronomy 210, spring semester 2016
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.
"This might not be considered interesting, but the different nebula colors are pretty cool. It's crazy what goes up there."

"The nebulae and the causes of their different colors."

"The H-R diagram--I just wish I knew how to use it."

"How the colors red and blue mean the opposite of what we are used to. Hot and cold."

"That you can use stellar luminosities to determine the diameters of the stars."

"I enjoyed learning about some of the nebulas. It was cool to learn about how they are made and why the appear to be the colors that they are."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Cold fusion--I don't know where to even start."

"The whole fusion thing was a little confusing."

"Some aspects of fusion were confusing for me."

"The difference between the different nebulae."

"I'm not really sure if there was anything I found confusing."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [83%]
Medium-mass (sunlike): medium luminosity [83%]
Low mass (red dwarf): dimmest luminosity [100%]

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 [67%]
Medium-mass (sunlike): medium fusion rate [83%]
Low mass (red dwarf): slowest fusion rate [75%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
 break heavy elements apart. ** [2] create convection currents. * [1] overcome gravity. * [1] overcome repulsion. **** [4] (Unsure/guessing/lost/help!) **** [4]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"It wouldn't cause the protons to move fast enough and collide."

"In order for fusion to actually happen, you need heat. Because heat is what makes the atoms move at a faster rate. otherwise they won't fuse together."

"Without the presence of high heat, the nuclei would not have enough speed to cause the violent collisions necessary to cause the needed reactions."

"I don't know."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [67%]
Reflection: blue [67%]
Dark: brown/black [75%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [67%]
Reflection: small dust particles [75%]
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.)
Medium-mass (sunlike): medium main-sequence lifetime [83%]
Low mass (red dwarf): longest main-sequence lifetime [75%]

If there was an open invitation to a house party (no specific time given), when would you show up?
 Early, or on time. ***** [5] When the most people should be there. ****** [6] After most everyone has left. * [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Wikipedia helps." (Wikipedia don't lie.[citation needed])

"I'm in a cabin trying to not lose more points in your class." (A Cabin...in the Woods?)

"What you taught us [Stefan-Boltzmann law] on Thursday made so much sense, I actually understood it!"

"Everyone loves a good house party."

"I'm that person that always arrives awkwardly late to house parties. Not intentional. Just always happens." (Always late, but worth the wait, right?)