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

Astronomy 210, fall 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.
"Fusion energy is really exciting, if we can start using it efficiently on Earth."

"Stars in stars clusters being born in the same time yet some stars age faster than others. I would assume they would age alike."

"The nebulas. Each having their own color and material was something new to me."

"I really enjoyed reading about the nebula clouds and am enjoyed learning what makes them beautiful colors."

"How stars form from the gaseous nebula clouds. Because it is so cool (or maybe hot) to see how something as large and hot as a star forms in somewhere as cold as space."

"I find your house party analogy actually really interesting and helpful. It adds a lot of humor to the lecture."

"How we get to talk about cheerleaders!"

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"H-R diagram--unsure how to properly interpret it."

"The technicality of how the nebula's form as well as cold fusion."

"I am having a hard time understanding why there is no mass/luminosity correlation for non main sequence stars."

"Confused on fusion rates compared to different stars."

"I found the colors of the nebulae confusing."

"Not much is confusing."

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 [82%]
Low mass (red dwarf): dimmest luminosity [82%]

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 [88%]
Medium-mass (sunlike): medium fusion rate [82%]
Low mass (red dwarf): slowest fusion rate [94%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  * [1]
create convection currents.  ** [2]
overcome gravity.  * [1]
overcome repulsion.  ********* [9]
(Unsure/guessing/lost/help!)  **** [4]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Because there must be enough heat for the molecules to overcome the Coulomb barrier (the fact that two positive charged nuclei repel each other), and collide with each other."

"It's impossible since the atoms wouldn't move fast enough to produce enough energy and would not overcome repulsion."

"Fusion requires heat, therefore 'cold fusion' wouldn't ever work."

"I can not at this moment."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [65%]
Reflection: blue [77%]
Dark: brown/black [82%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [88%]
Reflection: small dust particles [88%]
Dark: large dust particles [77%]

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 [65%]
Medium-mass (sunlike): medium main-sequence lifetime [88%]
Low mass (red dwarf): longest main-sequence lifetime [71%]

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.  *********** [11]
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 stars and nebulae eventually use up all the interstellar medium?" (Yes, but the accelerating expansion of the universe would probably overcome the tendency for interstellar gas and dust to gather together.)

"Is fusion the energy source for all stars or just the sun?" (Hydrogen fusion is the energy source for all main-sequence stars, including our sun. After the hydrogen is used up, then the star will begin to die as it attempts to restart fusion with heavier elements to provide energy.)

"Is there going to be an astronomy house party?" (#smh)

"I can bring chips."

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