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

Astronomy 210, fall 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.
"The fusion process--I think it is interesting to know what causes the heat and light from the stars."

"Mst stars are born at the same time but age differently."

"Stars have automatic pressure-temperature thermostats. These are used to regulate temperature and pressure so the star can maintain stability. I find this process really crazy!"

"Smaller stars will live longer because they conserve their fuel better. I would have thought that bigger stars would live longer."

"Nebulae between stars could create more stars itself."

"Pink clouds = hydrogen :)"

"Hydrogen is squished together to form helium, I had no idea this was possible."

"Different nebulae always appear as certain colors."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Hydrostatic equilibrium."

"Cold fusion."

"How mass could be formed into a star from the interstellar medium. What created the interstellar medium and how is it possible for it to form into a star? This was confusing because as I learn about astronomy many explanations for interesting things are vague or left out altogether making it confusing."

Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart.  ****** [6]
create convection currents.  **** [4]
overcome gravity.  *** [3]
overcome repulsion.  ****************** [18]
(Unsure/guessing/lost/help!)  [0]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"The gas must be very hot in order for the nuclei to have violent collisions and overcome the Coulomb barrier (repulsion), therefore room temperature would be implausible."

"Atoms all hate each other so the only way to make them collide and fuse to heat them up to millions of degrees so they're going so fast they don't notice before it's too late. They don't actually hate each other the charges of atomic nuclei just naturally repel other nuclei cause they're both mostly positive."

"The amount of energy required for fusion to occur would indefinitely raise the temperature, there is no way around it."

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 [77%]
Medium-mass (sunlike): medium fusion rate [87%]
Massive: fastest fusion rate [74%]

Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [81%]
Reflection: blue [77%]
Dark: brown/black [90%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [87%]
Reflection: small dust particles [84%]
Dark: large dust particles [84%]

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.  ************************* [25]
After most everyone has left.  [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I realize that the sun fuses four hydrogen nuclei to make one helium nucleus, but why does some mass 'vanish' in the process? Also where does it go?"(Albert Einstein's E = m·c2 equation says that you can convert mass into energy; since the helium nucleus has less slightly mass than the four hydrogen nuclei used to build it, the energy released from this process came from the mass that 'vanished!')

"Are you throwing a house party? I'll bring cookies."

"So, was Mrs. P-dog a cheerleader?" (Yes. In my dreams.)

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