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

Astronomy 210, spring semester 2018
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.
"You always use cool things to compare it to like using a car mpg/tank/range comparison to a main-sequence lifetime."

"Hummer/SmartCar anecdote. It really messed with my perspective."

"The Hummer vs. SmartCar analogy, because the car scenario makes sense and seems like it would transfer over to the stars, but it just doesn't. It gives me a new appreciation for the low-mass stars."

"We can't compare cars to stars. Stars are completely different and store energy different."

"That many smaller stars will outlive the sun."

"To discover that the bigger stars die faster than the smaller ones. This makes sense as the bigger stars have faster fusion rates which means that the run out of hydrogen faster. The smaller ones fuse at a slower rate and therefore take longer to die and this makes sense to me."

"I think it's amazing that not a single red dwarf star has died of old age anywhere in the universe! Thats how old they can be."

"That the larger the star the shorter the lifetime. I always would have thought the opposite for some reason."

"The death of stars--I think it's cool that the mass of the stars affects the way in which a star may die."

"To find out how stars die and about the white dwarfs and how they die alone. RIP."

"Nova explosions--it's hard to believe that something like that takes place in this universe!"

"The subject of star death. I have often heard people use the term 'supernova' before, but never really thought anything about it other than the fact that it was some form of explosion. So while I have always known what it really refers to on a very, very basic level. But really being able to see all the visuals and learn about the different types of star deaths was just really interesting to me personally. However, I am having a hard time pairing the right explosion with the stars they go with."

"The video link of the stacked ball drop. I had never seen nor heard of this. It was then easier to image the core implosion-explosion giving me a visual to see."

"Pulsars, because they're described as mysterious signals...cool."

"I found the mass difference of stars and black hole fascinating. The concept of black hole is so popular, yet so unknown."

"Reading about what black holes are and how they work."

"That black holes are not visible at all but you can still tell it's there."

"To learn about what would happen if you jumped into a black hole. I just thought this was cool because when I was a kid me and my friends would constantly talk about jumping in black holes like it was some joke and it was nice to learn, or at least get the idea of what would actually happen if you did that."

"'Spaghettification.' I've been anxious to learn a little more about black holes, so knowing that it would seem to be an infinite amount of time to an observer before something falling in circles and enters the event horizon is super interesting and scary to me."

"I found black holes quite interesting, specifically the way gravity works in black holes. The way space-time works and how the object going into the black hole looks to observers is very strange."

"Nothing really."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"How at the end of a medium-mass stars lifetime that it becomes a giant before it dies off. Wouldn't it just get smaller as it dies?"

"How a white dwarf can steal hydrogen from a neighboring star?"

"Novae were confusing. I don't really get how a white dwarf is able to siphon off the energy from another star."

"That stars actually die--they have a life, they live their life, and then they die?"

"Matching the end-of-life stage with the corresponding main-sequence star mass."

"Navigating the deaths/explosions of specific stars and could use in-class clarification."

"Having a hard time sorting through the information to compartmentalize each actual stage and pairing it with the star it goes with. "

"The process by which heavy elements are created."

"How a supergiant can implode-explode? I understand the concept of exploding but the idea of a star imploding first confuses me."

"When type II supernovae make heavier elements and ultimately explode, how do these heavier elements get all the way to us?"

"Density confuses me so much, so if you can explain it in class that would help a lot."

"How do they know exactly what happens in a black hole if everything is ultimately destroyed?"

"What black holes really do."

"Nothing was confusing to me, it was all pretty straightforward"

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 can hold more gas, but uses it more quickly, so it evens out."

"A Hummer H2 and a SmartCar ForTwo can travel the same distance on a full tank of gas because of the differences in their fuel capacity and efficiency. The Hummer is an extremely inefficient car, but to compensate for that fact it is made with an extremely large gas tank capable of carrying a lot of fuel. The SmartCar is a much smaller car, and while it's many times more efficient than the Hummer, it has a proportionally appropriate much smaller gas tank. Because of the differences in how much fuel these cars use and how much they can carry, despite their major size difference, they both end up having the same range."

"The Hummer H2 contains a larger tank for the gas therefore is able to hold more gas, and SmartCar ForTwo has great mileage but the gas tank is significantly smaller therefore cannot hold much gas. so the two cars travel the same distance."

"The Hummer would need to make more pit stops to refuel?"

"They both have the same size gas tank?"

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)
Black hole: massive main sequence star [76%]
Neutron star: massive main sequence star [43%]
White dwarf: medium-mass main-sequence star [41%]
(No stellar remnant observed yet): low-mass main-sequence star [38%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)
Type II supernova: massive main sequence star: [73%]
Type Ia supernova: medium-mass main-sequence star [65%]
Nova: medium-mass main-sequence star [43%]
Low-mass main-sequence star: (no explosion possible) [54%]

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.  ** [2]
days.  [0]
a year.  [0]
many years.  *** [3]
forever.  ************************* [25]
(Unsure/guessing/lost/help!)  ** [2]

The first rule of astronomy class is...
"Bring snacks?"

"It's boring but important?"

"Shoot for the stars?"

"Always pay attention?"

"Show up?"

"Do the reading assignments?"

"Ask questions?"

"Look up?"

"Having fun learning about space and our universe?"

"To be informed of and to abide by all student policies, and to call you P-dog?"

"Do your work every week?"

"Try your hardest?"

"What P-dog says, goes?"

"I don't remember. Don't die?"

"Do not talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Why isn't the carbon-oxygen core of a white dwarf not hot enough to convert the carbon and oxygen into heavier elements? (Even though the temperature is really hot, it doesn't have enough pressure/gravity to squeeze carbon together to fuse, unless more mass is added to it by another star.)

"Is it possible for another star to move close enough to our sun to cause mass transfer and accretion disks?" (It's too late for that, it should have been a star that was born nearby at the same time as our sun.)

"Why don't pulsars collapse in on themselves?" (They don't have quite enough mass and gravity to crush themselves into a zero-size black hole, but they did have enough mass and gravity to crush all their atoms and compact them into neutrons.)

"I know that in the in-class work we will have to fill in a stellar evolution chart, the topic is still feeling way over my head. I'm sure you will go into more detail about it before we do the assignment, but I just thought I'd put it out there."

"What were to happen to an object that we observe going into a black hole? Would we ever see it come out the other side or would the black hole appear to change?" (We won't ever be able to see what happens to the object after it enters the event horizon surrounding the black hole (as no light from inside the event horizon can escape). However, we would then wind up with a black hole that has slightly more mass and gravity.)

"What is our next quiz going to be on?" (This stuff--the birth, lives, and deaths of stars.)

"Is the final exam going to be cumulative? (Yes, but selectively cumulative, not "everything cumulative." You'll be given a definitive list of things on a study guide, and if something's not on that list, then it's not on the final exam.)

"Would you jump into a black hole to potentially live...F-O-R-E-V-E-R...rrrr?" (I don't think I'd enjoy the spaghettification process. Technically, you'd definitely die, it's just that no one would live long enough to be able to watch the process complete itself.)

"How was your spring break?" (Mrs. P-dog and I had an awesome time in the mountains. How about yours?)

"'sup?" (Chilling. You?)

"I plan on studying more."

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