20151103

Online reading assignment: medium-mass stars, massive stars, neutron stars and black holes (NC campus)

Astronomy 210, fall semester 2015
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 the evolution of medium-mass stars, massive stars, neutron stars and black holes.


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.
"Black holes are really interesting because they are mysterious. It will be cool to see how much we are able to discover about this during our lifetimes."

"That no low mass stars have died yet. How do we know this?"

"How the outer layers of the medium-mass star will expand and cool. Also, as a medium-mass star depletes the helium in its core, the outer layers keep expanding and will dissipate outwards."

"It was pretty cool that red dwarf lifespans are about 56 billion years, which means no red dwarf has yet to die since the universe is not that old. Pretty crazy to think about! I also thought it was kind of depressing to read about the inevitable death of the sun. I know its about 5 billion years away but its still scary to think about!"

"Black holes are so sick and mysterious!"

"That stars can change. I always assumed that a certain star would stay the same until it dies but they can change."

"I find the death of stars interesting because of what they turn into."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"One thing I found confusing is that the smart car could have better milage and a bigger gas tank, like a star. How does this work?"

"The lighthouse model of a pulsar."

"Space-time. I just can't wrap my head around how the gravitational forces work."

"How can they tell the age of a star?"

"I understood the stages of stars, but was lost when it came to the explosions."

"Masses vs. explosions. Which mass gets which explosion????"

"Comparing fusion rates between a medium mass star and a low mass star."

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.
"The Hummer has a much bigger gas tank."

"The SmartCar does things to burn the gas faster."

"It's possible because although the smart car gets more miles to the gallon, the Hummer has a much larger tank. Both cars will travel the same distance on a full tank but you'll spend a heck of a lot more on gas driving t"

"Still some confusion about this."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)
Black hole: massive main sequence star [74%]
Neutron star: massive main sequence star [17%]
White dwarf: medium-mass main-sequence star [43%]
(No stellar remnant observed yet: low-mass main-sequence star [65%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)
Type II supernova: massive main sequence star: [78%]
Type Ia supernova: medium-mass main-sequence star [57%]
Nova: medium-mass main-sequence star [57%]
Low-mass main-sequence star: (no explosion possible) [61%]

If you were to leap into a black hole, your friends would typically watch you falling in for __________ before you entered the event horizon.
seconds.  ***** [5]
hours.  * [1]
days.  ** [2]
a year.  * [1]
many years.  *** [3]
forever.  ******** [8]
(Unsure/guessing/lost/help!)  *** [3]

The first rule of astronomy class is...
"LOVE P-DOG."

"I don't know the rule. What rule?"

"Don't jump into black holes."

"Do your homework."

"Read the presentations."

"Go to class, study, and don't procrastinate."

(Don't talk about astronomy class.)

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"The black hole topic makes my brain hurt. Can you explain further in class how the whole time warp situation works."

"I thought I was understanding but now I am feeling lost. I think when I read it at home I confuse myself verses you saying it out loud in class. Please continue to go over the presentations in class."

"How have people notice black holes if we could only 'feel' them, do we notice a shift in background star positions behind a black hole?" (Yes, it's called gravitational lensing.)

"So, basically the sun is going to kill my future grandchildren." (Only if they're not smart enough to invent space travel.)"

"Can I ask you a question? (You just did.)

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