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

Astronomy 210, spring semester 2017
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.
"It's interesting to see what happens to a star when it dies, especially how the ending stage depends on the star's original mass. It is just such an edgy topic, and it's very entertaining to discuss."

"I liked how you used the AstroBlaster in reference to how a type II supernova works. Along with the basketball and tennis ball analogy. It really puts things visually into perspective for me."

"The way a nova can explode over and over was cool because it has a steady source of hydrogen from a companion star."

"A way to find a black hole is by looking for a strong source of x-rays."

"Learning about the types of novas because I honestly didn't know what they were before."

"I've always been fascinated with the concept of black holes. It was good to learn more about them and clear up some of the misconceptions I had."

"The Hummer and the SmartCar--how the big car and small car have the same range. I would expect the Hummer to have more than the SmartCar."

"I think it is interesting that pulsars can be picked up by radio signals!!!"

"Spaghettification. Mostly because no one has ever believed me that it is a thing, and it was the first really abstract thing I learned about space."

"How medium-mass stars only convert hydrogen to helium then die, while massive stars convert hydrogen to helium to carbon to oxygen to silicon and lastly to iron and then dies. I like chemistry so it was interesting reading the elemental processes they undergo."

"That if you jump into a black hole, for yourself it would take two months, but from the point of view of your friends it would take years. I don't know much about black holes but that was pretty interesting."

"Learning about black holes, and how the presentation slides described what you can't see."

"The different ways different stars die, some create something else with their death."

"Reading about stars dying was pretty interesting!"

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Neutron stars were a very confusing topic. The pulsars and lighthouse model were very difficult for me to understand."

"Black holes and how spacetime works."

"Jumping into a black hole and having your friends watching you."

"Learning about end of life stages in stars, but I just need to go over it a little more and I'll have it down."

"Ironically, the section on black holes was not only the most interesting, but also the most confusing. I have a hard time wrapping my head around some of the concepts, especially the 'spaghettification' and time dilation."

"Something confusing for me would be understanding a little more about the massive, medium-mass, low-mass, between a white dwarf, nova, black hole, etc."

"I am a bit confused on solar masses. Im not sure how to compare the sizes or how to remember which number of solar masses falls under which categories of star sizes."

"Spacetime curvature. I think I grasp the general concept, but I feel like there are some things that weren't covered that would let me know I am actually grasping it."

"I found the neutron stars a little confusing, like I get that they give off pulsars but can you see them? And how do black holes not have a determined size?"

"I found that figuring which stars were low/medium-mass/massive stars was kind of difficult, but the chart that was given to us helped a lot."

"Black holes--even though I found them superinteresting I don't understand the purpose they serve or what happens to them."

"The idea of black holes and if you were to jump into them. It was confusing to me where it talked about if you jumped into the black hole, you would be gone. But your friends watching you would see you slowly heading towards it. Why?"

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.
"Although a SmartCar has way better mileage than the Hummer, the Hummer has a larger tank for gas. The SmartCar burns gas slower but it holds less gas, and the Hummer burns gas faster but it holds more gas. The gas mileage and capacity of the two sort of balance out, allowing them to travel the same distance with a full tank."

"The gas tank size averages out with the mpg to travel the same distance."

"Although both cars are able to travel the same distance with a full tank, the Hummer requires a larger fuel tank in order to compensate for mileage."

"The Hummer has a larger gas tank and carries more fuel. the SmartCar will get more miles to the gallon but can't carry a lot of fuel."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)
Black hole: massive main sequence star [94%]
Neutron star: massive main sequence star [50%]
White dwarf: medium-mass main-sequence star [56%]
(No stellar remnant observed yet: low-mass main-sequence star [56%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)
Type II supernova: massive main sequence star: [88%]
Type Ia supernova: medium-mass main-sequence star [88%]
Nova: medium-mass main-sequence star [56%]
Low-mass main-sequence star: (no explosion possible) [63%]

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.  *** [3]
hours.  [0]
days.  [0]
a year.  [0]
many years.  ** [2]
forever.  ********* [9]
(Unsure/guessing/lost/help!)  ** [2]

The first rule of astronomy class is...
"Call you P-dog."

"Always ask questions."

"Be open-minded! Some of the things we learn are going to be harder to understand if you're close-minded!"

"To pay attention and do your homework."

"Show up on time and prepared."

"Come to class and bring your starwheel."

"Do your homework--not really but I couldnt find the answer you wanted."

"Have miso soup?"

"Don't talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I am still confused about black holes and how long it takes before entering the 'event horizon' the point of no return. Is it forever?" (From what an outside observer would see, yes, but for you falling in, it wouldn't take very long.)

"Spagettification, for me, begs the question: does it actually take a long time or did it already happen a long time ago and light takes a long time to escape? Does it distort time at all?" (Yes, and yes.)

From what I was understanding from the reading, a white dwarf is a remnant of a medium-mass star. I guess it seems a little confusing because the medium-mass star dies but then on lives the white dwarf??? So is the white dwarf only formed after the medium-mass star dies?" (When a medium-mass main-sequence star begins to die, it sheds off its outer layers (as a planetary nebula), and the the exposed core that is left over is what becomes a white dwarf. So it's like the "skeleton" of a medium-mass star.)

"Why do we study the life of a red dwarf star if we don't know how they die or the fact they none of us will witness this one ever. Then why study it?" (Some scientists like to ponder the imponderable.)

"I absolutely love everything to do with life beyond Earth but I feel like unless I had an 'in' somewhere, it would be difficult to find a way into this career field."

"Ultimately will black holes suck in everything?" (No, most still have the same mass as the core of their original star, so they have the same amount of gravity. Traveling around the galaxy, you're just as susceptible to the gravitational pull of a black hole (the remnant of a star) as the gravitational pull of a star that is still living.)

"What is the first rule of astronomy class?"

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