Online reading assignment: fusion, nebulae, star cluster ages (SLO 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.
"Molecular clouds because not only are new stars are born, but the dust can form planets. This is cool."

"I thought the cheerleader analogy was interesting!"

"That there are only three colors in space."

"How the more pressure there is within a star increase the fusion rate, which thus makes the star brighter and more luminous. I found this interesting because I never really knew what 'fusion' meant."

"Giants and supergiants having a very low-density--I would have expected something big to be more dense."

"That small stars have a longer life span than big stars--I thought it would be the other way around."

"Comparing the stars to people going to a house party."

"I found it interesting how fusion increases as heat and pressure increase. I had always wondered what causes fusion to occur."

"The lifetimes of the stars, and why they die."

"Why different sizes of stars have different luminosities."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The different types of nebula. How do we tell the difference?

"I don't understand why white dwarfs don't relate to the same rules about mass and luminosity as main-sequence stars."

"Learning about nebulas because I didn't really know what they were or what the colors meant."

"Layers in the hydrostatic equilibrium had me a little lost."

"Why clouds of hydrogen emit a pink color. This is because I don't understand the nature of light and hydrogen."

"That some stars obey the mass-luminosity rule, while others don't, because it seems like there's a lot of exceptions to these rules we learn."

"The evolutionary tracks of different stars are a bit confusing just because there is so much going on!"

"I did't find things that complicated this time. This was pretty informative and went straight to the point."

"Pretty much all of it this time."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [96%]
Medium-mass (sunlike): medium luminosity [100%]
Low mass (red dwarf): dimmest luminosity [96%]

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 [83%]
Medium-mass (sunlike): medium fusion rate [96%]
Low mass (red dwarf): slowest fusion rate [88%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  **** [4]
create convection currents.  ** [2]
overcome gravity.  ***** [5]
overcome repulsion.  ********************************* [33]
(Unsure/guessing/lost/help!)  **** [4]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Cold fusion is implausible because fusion can only happen under extreme temperatures and high pressure."

"The protons wouldn't move fast enough to be able to bump into each other."

"High temperature is required to force protons to collide and produce energy. At room temperature, protons hate each other like Taylor Swift and Kanye." #immaletyoufinish

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [81%]
Reflection: blue [85%]
Dark: brown/black [90%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [90%]
Reflection: small dust particles [85%]
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.)
Massive: shortest main-sequence lifetime [71%]
Medium-mass (sunlike): medium main-sequence lifetime [96%]
Low mass (red dwarf): longest main-sequence lifetime [73%]

If there was an open invitation to a house party (no specific time given), when would you show up?
Early, or on time.  ************ [12]
When the most people should be there.  ************************************ [36]
After most everyone has left.  [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"How have we learned everything we know about about stars--they are so far away? Like, how do we know their composition?" (We know what stars are made of from analyzing the absorption lines in their spectra. Their colors tell us their temperatures, their parallaxes tell us their distances, and we can also calculate their sizes as well.)

"How does fusion have an effect on a star's luminosity?" (For main-sequence stars, its luminosity (bright or dim) is related to the rate of energy released by fusion in their cores (rapid or slow).)

"I found the stars that do not obey the cheerleader model [supergiants, giants, and white dwarfs] a bit confusing. How does the mass not affect their luminosities?" (All main-sequence stars (massive, medium-mass, and low mass) produce energy by fusing hydrogen, but at different rates related their masses. Supergiants, giants, and white dwarfs are actually stars that have used up their hydrogen, so they are either dying or dead, so their masses don't relate to their rate of energy production.)

"All of the examples for this section were awesome! I love the nebula photos because they are so pretty and intriguing to stare at. But I also love the house party because the analogy is funny and totally helped me understand!"

"Yes, I would come to your awesome house party. I would arrive early and stay late." (Keep in mind that the house party is just an analogy for different star lifetimes.)

"When is the house party? I'll bring chips and salsa." (The chips and salsa are an analogy for what, exactly?)

"When do you show up to parties? Early, on time, when most people are there or when mostly everyone has left?" (I am always late, but worth the wait. #youshouldbehonoredbymylateness)

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