Sketchbook: low-mass stars

The sun introduces some other low-mass stars. Also, the sun's expressions pretty much sums up how I feel about things right now.

Somehow I associate "low-mass" with "low-key."

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

Astronomy 210, fall semester 2019
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.

"I found the car example to be really interesting. It's cool how we can relate real life things to this subject."

"How the stars can live off of helium after they have depleted all of their hydrogen."

"That helium fuses into heavier elements when it reaches a higher temperature of 100,000,000 K. Chemistry is my favorite subject and I was just very intrigued at that."

"Supernovas are fascinating because they are one of those 'doomsday' events that the sci-fi genre tends to romanticize."

"How in a binary star system, a dying star will begin 'eating' the fuel of its companion star. And if it 'eats' too quick it will explode and kill itself and its partner."

"How sad some white dwarf stars are alone. It's pretty depressing that they starve to death and die alone."

"That when medium-mass stars die they become white dwarfs, and then with a companion star go on to either become a nova or a type Ia supernova."

"The way a white dwarf can suck the hydrogen from a companion star is amazing."

"The death process of the stars, especially, the type II supernova. I did not know anything about how stars die, why they die, and what they become after death."

"Core implosion/explosion is very fun to learn about. I can imagine the outer layers of the star being gravitationally forced to crush the inner core. I can imagine that type II supernova star explosion being fairly colorful and dusty."

"I spent almost my entire high school career researching the death-cycle of stars for my senior project. WAY cool."

"That it would take forever watch something get into the black hole. And the spaghettification effect."

"How black holes can make bipolar jets! That's cool."

"I was always curious as to how black holes formed! They are just so... ominous. I would not want to get near one--they're freaky!"

"I thought this whole lesson was super-interesting, guess I'm goth-ier than I realized haha."

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

"Why a Hummer and a SmartCar can travel the same distance if a Hummer has a larger tank and a SmartCar has a smaller tank."

"Corresponding the correct end-of-life stage to the correct main-sequence star is a bit confusing at first because white dwarfs have technically low mass, but they become one after their medium-mass star depletes its hydrogen and becomes a giant that turns into a white dwarf after all its energy has been exerted."

"Why do massive stars eat anything they can to survive but smaller stars won't eat as much junk?"

"I need more explanation on a star's death and the phases the star takes as it dies."

"How it is possible for a white dwarf (with a companion star) to either flash-fuse or just simply explode. How can it do one or the other? Wouldn't it just do one every time?"

"As much as black holes intrigued me, they also confused the hell out of me. Trying to understand the physics of it all was pretty difficult."

"Time slowing when approaching a black hole's event horizon."

"I'm having trouble wrapping my head around the idea of black holes--why they can't be seen, event horizons, space-time, etc."

"Why the space-time grid is always depicted as a flat surface. I just don't get we they do that. Is it to make it easier to conceptualize?"

"When talking about black holes in space, I understand that we would be able to feel a black hole because of the gravitational pull inward toward it. I'm confused about how the black hole effects space-time."

"A bit of everything since it's all so much to take in."

"Nothing particularly was confusing."

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 fuel usage for a SmartCar is way lower than the fuel usage of a Hummer, but a Hummer has way more fuel available to it than the SmartCar."

"A Hummer has a larger tank with lower gas mileage while the SmartCar has a smaller tank with higher gas mileage. These factors balance each other out between the two cars and give them both the same traveling distance."

"The Hummer could have a bigger gas tank than the SmartCar. And the SmartCar would have better gas mileage."

"The Hummer can hold a lot of gallons of gas, but it burns through it very quickly (bad gas mileage). A SmartCar doesn't hold very many gallons but burns through it very slowly (good gas mileage)."

"I'm kind of confused on how to explain this. It didn't make sense to me at all."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)

Black hole: massive main sequence star [92%]
Neutron star: massive main sequence star [76%]
White dwarf: medium-mass main-sequence star [80%]
(No stellar remnant observed yet): low-mass main-sequence star [72%]

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 [92%]
Nova: medium-mass main-sequence star [56%]
Low-mass main-sequence star: (no explosion possible) [56%]

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.	* [1]
hours.	** [2]
days.	* [1]
a year.	[0]
many years.	* [1]
forever.	***************** [17]
(Unsure/guessing/lost/help!)	*** [3]

The first rule of astronomy class is...

"Show interest in space."

"Observe the world around you."

"To actually show up and attend class!"

"Don't procrastinate."

"Question everything you thought you knew."

"Read the syllabus and get your starwheel."

"I'm not too sure. Show up early? Wear old clothes? Bring a sledgehammer?"

"A foot-measuring device is for feet only."

"I feel like this was a trick question and I searched the text for it, but ultimately just ended up confused. The first rule is to learn to the best of your abillity?"

"You do not talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I need a lot of explanation on the main sequence stars and explosions, plus how the lifetimes work."

"Dying stars are cool."

"Was our solar system (planets, asteroids, etc.) created by another star or from our sun? If by a different star, where is that star now?" (Anything other than hydrogen in our solar system was created by massive stars that exploded a long time ago (we don't know where those first-generation stars that lived and died are anymore). Then when our sun starting forming out of unused hydrogen from those previous stars, it gathered up the elements created by those stars around it to make the planets. #deepthoughts)

"Talk about black holes, I can't get enough."

"'Spaghettification' is my new favorite word."

"Do you like Star Wars? (Well, probably just the original trilogy. And maybe Rogue One.)"

"What is "nothing"? Can there be such a thing? I just watched '2013 Isaac Asimov Memorial Debate: The Existence of Nothing' and now my brain hurts and I'm not satisfied with the answers given there." (Now you're making my brain hurt. #deepthoughts)

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

Astronomy 210, fall semester 2019
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.

"How a low-mass star will take much longer to run out of hydrogen to fuse. How does it take longer, since it's smaller? "

"How a Hummer and SmartCar are able to travel same distance even with the Hummer having a larger tank."

"The lifetimes of the stars. I just find it cool how it's the bigger stars that burn out and die off the quickest compared to the small stars who live on for much longer."

"In a long time the sun will eventually expand into a red giant and that is when Earth will come to an end."

"That a star's mass determines what happens when the star runs out of fuel, and what type of 'corpse' it will become after its death."

"That when a star is about to die it goes into 'starvation' mode."

"Learning more about stars like our own really puts our existence into some perspective."

"That different mass stars die different ways, because I had just assumed that they would just stop glowing, but I was way wrong."

"The types of supernovas/novas, because those were cool images."

"Black holes."

"Black holes are invisible, kinda ominous and scary, but interesting nonetheless."

"The escape velocity of a black hole blows my mind that even light cannot escape."

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

"How convection currents work internally in the stars."

"I'm confused about binary systems and how they keep going even after the nova that occurs from the white dwarf."

"I'm not grasping the different types of supernovas/novas."

"The lighthouse model! What is it trying to explain?"

"Black holes and neutron stars. I don't know the models made a little sense but I think spending a little more time on it and further explanation on it that would help because I am a little lost."

"How a black hole works."

"Nothing in particular."

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 H2 has a bigger gas tank but uses it faster. The SmartCar has a smaller gas tank and uses it slower."

"The Hummer has lower mileage than the SmartCar but, it has a bigger fuel tank."

"It's possible because the SmartCar has better fuel efficiency with its smaller tank."

"I honestly don't know; I'm slightly confused."

"Don't know yet."

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 [59%]
White dwarf: medium-mass main-sequence star [53%]
(No stellar remnant observed yet: low-mass main-sequence star [35%]

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 [82%]
Nova: medium-mass main-sequence star [35%]
Low-mass main-sequence star: (no explosion possible) [53%]

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.	** [2]
hours.	* [1]
days.	[0]
a year.	[0]
many years.	* [1]
forever.	********** [10]
(Unsure/guessing/lost/help!)	*** [3]

The first rule of astronomy class is...

"Persistence?"

"Ask questions?"

"Earth is flat?"

"To build telescopes?"

"Come to each and every class?"

"Dome prepared and ready to learn?"

"Look up at the stars, because that is where the answers are?"

"You do not talk about astronomy class.' (Fight Club, 1999)"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"How are cars related to astronomy?"

"For a medium-mass star, how come the convection current doesn't work in the similar way a low mass star works?" (Convection is a surface effect for a star, so for a medium-mass or massive star, convection (the "miso soup effect") is right at the "skin" of those stars. However, for a low mass star, it is so small that the "skin" and core are basically touching, such that the convection currents are able to affect the core.)

"What is space-time and how can gravity affect it?"

"I'd like to go over black holes a bit more."

"Will we get into black holes more or will we just get a brief talk about them?

"Have humans ever sent anything into a black hole?" (No, but we have observed stars being shredded apart as they get too close, and their material falls in towards black holes.)

"Can you please go over these slides in class, there was a lot, thank you."

Astronomy quiz question: A5 white dwarf vs. G5 supergiant

Astronomy 210 Quiz 5, fall semester 2019
Cuesta College, San Luis Obispo, CA

An A5 white dwarf has a ___________ than a G5 supergiant.
(A) brighter luminosity.
(B) larger size.
(C) hotter temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (C)

An H-R diagram is provided with this quiz.


These stars are plotted on an H-R diagram below. The A5 white dwarf has a hotter temperature, but a dimmer luminosity and smaller size than the G5 supergiant.


Section 70158
Exam code: quiz05Sh0w
(A) : 2 students
(B) : 1 student
(C) : 20 students
(D) : 3 students
(E) : 2 students
(F) : 1 students

Success level: 70% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

(Cf. a re-worded version of this same question: "A G5 supergiant has a ___________ than an A5 white dwarf.")

Astronomy quiz question: B5 main sequence star vs. M5 giant

Astronomy 210 Quiz 5, fall semester 2019
Cuesta College, San Luis Obispo, CA

A B5 main sequence star and an M5 giant could have the same:
(A) luminosity.
(B) size.
(C) temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (A)

An H-R diagram is provided with this quiz.


These stars are plotted on an H-R diagram below. The B5 main sequence star has a smaller size and a hotter temperature than the M5 giant, but they could have the same luminosity.


Section 70158
Exam code: quiz05Sh0w
(A) : 22 students
(B) : 1 student
(C) : 0 students
(D) : 2 students
(E) : 1 student
(F) : 3 students

Success level: 77% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.63

Astronomy quiz question: G5 supergiant vs. A5 white dwarf

Astronomy 210 Quiz 5, fall semester 2019
Cuesta College, San Luis Obispo, CA

A G5 supergiant has a ___________ than an A5 white dwarf.
(A) brighter luminosity.
(B) larger size.
(C) hotter temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (D)

An H-R diagram is provided with this quiz.


These stars are plotted on an H-R diagram below. The G5 supergiant has a brighter luminosity, larger size, but a cooler temperature than the A5 white dwarf.


Section 70160
Exam code: quiz05NpRm
(A) : 1 student
(B) : 1 student
(C) : 0 students
(D) : 12 students
(E) : 6 students
(F) : 2 students

Success level: 56% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.71

(Cf. a re-worded version of this same question: "An A5 white dwarf has a ___________ than a G5 supergiant.")

Astronomy quiz question: B5 supergiant vs. K5 main sequence star

Astronomy 210 Quiz 5, fall semester 2019
Cuesta College, San Luis Obispo, CA

A B5 supergiant and a K5 main sequence star could have the same:
(A) luminosity.
(B) size.
(C) temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (F)

An H-R diagram is provided with this quiz.


These stars are plotted on an H-R diagram below. The B5 supergiant has a brighter luminosity, larger size, and a hotter temperature than the K5 main sequence star.


Section 70160
Exam code: quiz05NpRm
(A) : 5 students
(B) : 0 students
(C) : 0 students
(D) : 2 students
(E) : 1 student
(F) : 14 students

Success level: 66% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.57

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

Astronomy 210, fall semester 2019
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.

"I'm excited to learn more about how fusion works. It just seems cool."

"How fusion only happens in the core of a star."

"I appreciated the cheerleader analogy, it actually really helped to be able to visualize what's happening at the sun's core."

"It is fascinating that lower-mass stars last longer than the current age of our universe, although it makes sense because, effectively, they are 'burning' slower."

"I thought it was funny that big stars burn out faster. For some reason reminded me of sumo wrestlers."

"Luminosity depends on mass for only main sequence stars--I thought that would apply for all stars."

"I just found how main sequence stars are ordered by mass, however the other stars (giants, super giants, and white dwarfs) aren't. It just caught my attention."

"That after a star runs out of hydrogen it dies :("

"It's amazing that there is so much matter in space, I thought it was just empty space."

"I thought the nebulae were super-cool (and super pretty). It's kinda weird to think about there being 'clouds' in space, I like it though."

"That nebulae are different colors due to the way photons interact with gas/dust."

"How the different components of nebulae determine their colors."

"I found that when there are a cluster of stars and when dust is around from the stars they turn into little planets around the star. This was interesting to me because when you look at the picture of the star cluster it just looks like a bunch of stars."

"Supernovae are interesting because they can 'kickstart' the formation of new stars."

"Star formation was one of the things I was most curious about coming into this class. It's interesting to learn about the process."

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

"Fusion because there's big words and I am tired so my brains not really working if I'm being honest."

"I find the H-R diagram to be confusing at times. I think it has to do with the multitude of variables displayed. I thought I had it figured out last class, but then certain stars break from the mass-luminosity relationship. Conceptually that might have thrown me off some. My plan to further my understanding is to maybe ask for a walkthrough in class."

"I found the plotting of the other stars off the main-sequence a bit confusing because there's no correlation between their mass and luminosity."

"The main sequence lifetimes for different sizes of stars confused me for a little bit because I read it wrong when I first read it. At first I though the bigger stars would stick around the longest."

"Hydrostatic equilibrium and fusion."

"I'm not super-confused but would just like more practice with determining what is and isn't in a nebula."

"Learning about the different types of nebulae was a bit confusing for me. For the reflection nebula, it's hard for me to imagine how the cloud filters out the certain colors from the star hitting it. I don't understand how these nebulae behave differently in space based on their composition."

"The H-R diagram doesn't make sense to me, but I think I understand the house party model?"

"I don't understand the H-R diagram; specifically the turn-off point."

"It's all rather hard to grasp."

"Nothing in particular, what I read made sense to me. "

"I didn’t find anything confusing."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)

Massive: brightest luminosity [100%]
Medium-mass (sunlike): medium luminosity [96%]
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 [78%]
Medium-mass (sunlike): medium fusion rate [96%]
Low mass (red dwarf): slowest fusion rate [81%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:

break heavy elements apart.	***** [5]
create convection currents.	*** [3]
overcome gravity.	** [2]
overcome repulsion.	*************** [15]
(Unsure/guessing/lost/help!)	** [2]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.

"Because it is much more effective at higher temperatures. The collisions between nuclei would not happen at room temperature."

"Fusion requires high pressure and temperatures. When pressure and temperatures are low, then hydrogen does not get squeezed as much and it moves too slowly to collide with one another."

"Because hydrogen can only be fused if it is moving very fast and under lots of pressure for enough force to overcome proton-proton repulsion."

"The amount of pressure required would be ridiculous."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)

Emission: pink [93%]
Reflection: blue [93%]
Dark: brown/black [100%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)

Emission: hydrogen [96%]
Reflection: small dust particles [100%]
Dark: large dust particles [96%]

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 [67%]
Medium-mass (sunlike): medium main-sequence lifetime [96%]
Low mass (red dwarf): longest main-sequence lifetime [70%]

If there was an open invitation to a house party (no specific time given), when would you show up?

Early, or on time.	***** [5]
When the most people should be there.	********************* [21]
After most everyone has left.	* [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Why aren't the other types of stars ordered in terms of their masses on the H-R diagram?" (Because they're dying or dead stars that ran out of hydrogen in their cores.)

"I need more help on the H-R diagram and the mass and luminosity stuff."

"The H-R diagram is a little confusing to tell which stars have a higher/lower luminosity. From what I read the bottom stars have less right?" (Correct.)

"How do stars form from dust clouds? Or is it the hydrogen in the dust clouds that forms the stars? where does the dust come from in the first place?" (The universe started out with just hydrogen, which formed the first stars. Then after the stars fused hydrogen into other stuff, they they exploded, such that when subsequent stars can form (from the remaining unused hydrogen), planets can form around them from the "dust" that was produced from the previous generation.)

"My mind was blown when they said that there are more stars than grains of sand on Earth. That's insane! What's the method for counting all the grains of sand though?" (Count how many grains of sand in a handful; then estimate how many handfuls of sand there are...)

"So, when the Enterprise hides in a nebula from a Klingon warship (in the movie Star Trek II: The Wrath of Khan), wouldn't it be best for it to be a dark nebula, with the large clumpy dust particles? But then it shouldn't have looked like a big glowing cloud, right?" (You sound like you know way too much astronomy.)

"I found dark nebulas to be interesting. When I was thinking about it, the night sky is already dark. If you look at a long exposure photograph you could then see these dark clusters called dark nebulas. It's amazing that they are completely blocking a viewer on Earth from seeing some stars because of their thick dust clouds. My question is, can you see them with the naked eye, or only through photographs? I feel like I would have noticed a patch of the night sky missing by now." (There aren't any big dark nebulae close for us see them with the naked eye noticeably blocking stars, but if you do a time exposure so you can see faint, distant stars, you can make out a variety of dark nebulae that block out those really faint stars; those dark nebulae especially stand out with the Milky Way as a background.)

"Can a supernova be the birthplace of a black hole?" (It is, specifically a type II supernova.)

"Would you ever actually have a house party with your students to see who was truly honest about their answer on this assignment?" (That sounds like a science experiment to me.)

"You have any fun plans for Halloween?" (Mrs. P-dog and I celebrate Madonnaween.)

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

Astronomy 210, fall semester 2019
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 H-R diagram is great once you know how to read it."

"It was interesting to find out the luminosity, size and temperature for the stars using the H-R diagram."

"Big stars don't last as long as small ones, it makes sense but it just feel more right that because they're big it's a longer time for them to burn out."

"One thing I found interesting about main sequence stars is that the more massive they are, the more luminous they are."

"I had heard of nuclear fusion, but I didn't realize that was what fueled a star. It puts our efforts to replicate it here on Earth into perspective."

"Did not know that there were dust clouds in space that block out stars to where it looks like there is a black blotch."

"That there are different nebula as I was very vaguely informed on what one even was."

"Something that I found very interesting from this presentation was the notion of nebulas. Nebulas look like clouds in space but they serve a much larger purpose."

"How the reflection, emission, and dark nebula get their colors."

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

"Something that I found personally confusing was the part where it talked about fusion, I was confused because the presentation doesn't really go into depth as to how it works. If you could explain it that would be great."

"Cold fusion, I just can't wrap my mind around it. Hydrogen and its isotopes at room temperature dissolve into a specific solid at such a high concentration a strong nuclear force occurs and boom, cold fusion?"

"Lifetime of stars?"

"Interstellar medium. I think I have the base idea about it but I would how we were able to find the interstellar dust in the vacuum of space."

"Is this a trick question? Everything’s confusing before you understand it 🤷‍♂️."

"I personally found all the reading to be a bit of an information overload and hope to have a lot of things clarified by next class."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)

Massive: brightest luminosity [100%]
Medium-mass (sunlike): medium luminosity [100%]
Low mass (red dwarf): dimmest luminosity [100%]

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 [71%]
Medium-mass (sunlike): medium fusion rate [100%]
Low mass (red dwarf): slowest fusion rate [71%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:

break heavy elements apart.	***** [5]
create convection currents.	**** [4]
overcome gravity.	** [2]
overcome repulsion.	*** [3]
(Unsure/guessing/lost/help!)	[0]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.

"Under low pressures and temperatures, hydrogen does not get squeezed very much, and moves too slowly, they won't collide with each other."

"Because nuclear fusion requires high temperatures to overcome the natural forces that normally prevent that kind of thing."

"Due to the fact that nuclei which are positively charge would not collided with each other but would repulse each other so the atoms could not create energy."

"Fusion can't happen in cold temperatures because protons are positively charged and repel each other."

"Have no clue."

"I'm not sure."

Match the three different types of nebulae with their colors.
(Only correct responses shown.)

Emission: pink [86%]
Reflection: blue [86%]
Dark: brown/black [93%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)

Emission: hydrogen [86%]
Reflection: small dust particles [71%]
Dark: large dust particles [71%]

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 [64%]
Medium-mass (sunlike): medium main-sequence lifetime [93%]
Low mass (red dwarf): longest main-sequence lifetime [57%]

If there was an open invitation to a house party (no specific time given), when would you show up?

Early, or on time.	******** [8]
When the most people should be there.	***** [5]
After most everyone has left.	* [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Does interstellar matter dust turn into a planet or a star? Both?" (Yes, either is possible.)

"I found this survey a bit difficult and could really use extra help."

"The picture of the nebulae are cool and I think we show see more of them."

"Nebulae have amazing colors."

"I love learning about stars! They're one of the most fascinating subjects in astronomy for me, given that our star is the only reason we're even alive."

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

Astronomy 210, spring semester 2019
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.

"I think that everything in this presentation is interesting. Especially the pictures and GIF animations provided of what the life stages look like. It's not something a student outside of the astronomy class would see and understand."

"Comparing low-mass and medium-mass stars to a SmartCar and a Hummer. It made the analogy easier to remember."

"I found the H2 versus Smartcar example a great way to put this section into perspective. Not having great mileage but having the capacity to compensate for it."

"That a lower mass star can survive substantially longer than a larger mass star."

"I like the refrigerator analogy and 'star-vation.' It helped me understand the stages in which order a star will use certain fuels."

"I liked your refrigerator analogy about stars having to eat helium after all the hydrogen is gone because a star's got to eat, right?!"

"Stars from about the size of the sun could turn into giant stars and massive stars could potentially become supergiants. Red dwarfs are fully convective meaning that their life expectancies are extended."

"How if you open mouth breathe on your hand it will be warm, but if you purse your lips it will be cool. I found that it made the information easier to understand."

"That a medium-mass star becomes a giant."

"How different mass stars die differently."

"I found it interesting that the more massive the star the longer it keeps fusing. So after hydrogen it fuses helium into carbon, and if its massive it keeps going. I didn't know stars fused beyond hydrogen."

"That the energy generated in the core of a star is what opposes gravity and supports the star."

"I thought the information about how stars die was interesting because I didn't know the many ways they could go."

"That an entire star's life revolves around this single force that is gravity. The star is using gravity to create more energy for itself from its core to continue living, and at the very end, it has a life or death battle with gravity where it can either lose and become consumed in darkness, (black hole) or continue in peace in ultimate stability (neutron star)."

"I found it interesting that there are different types of supernovas: type Ia and type II."

"Massive star death. Probably one of the coolest things about the universe. Who doesn't like explosions?"

"Black holes and the effect it has on spacetime and what is around it. The fact that you can't see it but you can feel it is crazy."

"Black holes are very interesting because we do not know what they do and they are scary."

"Black holes, because what is even their purpose?"

"To see how there is a 'black hole' in Lake Berryessa. I don't know how to swim and just looking at the image makes me scared."

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

"I didn't understand the Hummer H2 and SmartCar question."

"There wasn't anything that was too confusing. At first I was a little lost with the car example."

"The medium-mass star stages. I'm a bit fuzzy on how a star that is losing its fuel source is increasing in size. Normally in most situations its the other way around. So I am curious to see how this works."

"The different types of (super)novae."

"Binary system explosions."

"Black holes, because they seem so complicated, how could we ever really comprehend what they actually are and do."

"How black holes work and what happens when something gets sucked into it."

"The event horizon of a black hole. I am unsure what the event horizon is even after reading the definition in the textbook I am still confused."

"Black holes were confusing. Everything about that section just went over my head."

"I can't really wrap my head around a black hole's time dilation. How do we know this exists?"

"I have a lot of questions. I'm sure as I listen to you explain it that will help though. I learn by listening."

"A little bit of everything was confusing. I got the main parts but some of it was slightly confusing."

"I did not find anything particularly confusing."

"Almost everything."

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

"Because the Hummer H2 has such low gas mileage it requires a bigger gas tank to get farther. The SmartCar has better gas mileage so it can get away with a smaller tank. One variable is increased while the other is decreased making the total distance even."

"The Hummer and the SmartCar have the same range but two different variables. The Hummer has a lower mpg and a larger gas tank. The SmartCar on the other hand has a high mpg with a small gas tank. Because the SmartCar has a higher mpg, it allows it to use fuel more efficiently. While the Hummer is not fuel efficient, it has to compensate by having a large fuel tank. But ultimately, both vehicles have the same range."

"They can travel the same distance because whilst the H2 having bad gas mileage, it makes up for it by having a large fuel tank to compensate."

"The Hummer has more gas in the car but it burns through it faster where the SmartCar can hold less gas but uses it more efficiently."

"I really don't understand this question."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)

Black hole: massive main sequence star [64%]
Neutron star: massive main sequence star [58%]
White dwarf: medium-mass main-sequence star [48%]
(No stellar remnant observed yet): low-mass main-sequence star [42%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)

Type II supernova: massive main sequence star: [76%]
Type Ia supernova: medium-mass main-sequence star [70%]
Nova: medium-mass main-sequence star [42%]
Low-mass main-sequence star: (no explosion possible) [55%]

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.	* [1]
days.	* [1]
a year.	* [1]
many years.	*** [3]
forever.	***************** [17]
(Unsure/guessing/lost/help!)	******* [7]

The first rule of astronomy class is...

"I don't know."

"Study?"

"Keep looking up?"

"Be intrigued by space?"

"Read the textbook materials and show up to class?"

"Pay attention?"

"You cannot see black holes by themselves?"

"To ask questions?"

"Prepare?"

"To have fun while learning?"

"To know the difference between astronomy and astrology?"

"Pay attention and do your reading because it's difficult?"

"Always bring a towel?"

"We have a rule?"

"There is no astronomy class?"

"Don't talk about astronomy class."

"Tell all your friends about astronomy class?"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I shared with my sister the house party model. She laughed!"

"I found the reading to be very confusing this week! The presentation slides somewhat helped."

"I am confused at the death of stars and their end-of-life stages. Would it be possible to go over those in class?"

"I would like to learn more about how gold is formed from a supernovae."

"What would be a dumbed-down version of explaining a black hole?"

"Could we go over the black holes section in more detail?"

"I'm good but thank you! Is there going to be another study session before the next midterm? (Yes.)

"Can we review what is going to be on the next quiz and exam in our next classes? (We will.)

"How much will we review as a class for the final?!?!?!?!?!" (The study guide for the final exam will be posted soon. But first get through the next quiz and the second midterm.)

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

Astronomy 210, spring semester 2019
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.

"I found the fact that low-mass stars take billions of years to die and spend so much time as a main sequence star. To think something like that has lived for so long is pretty cool to think about."

"How the Hummer H2 and SmartCar comparison was used to describe main-sequence lifetimes of stars, it made the material very memorable."

"The comparison between stars and cars."

"How giants cool as they expand. I tried the trick of blowing air on my hand the two different ways and it helped me understand what was being said more."

"The discovery of how stars will undergo 'star-vation' was interesting to me; seeing how stars can almost recycle the atoms they created until they are no longer usable."

"How massive stars undergo type II supernovae explosions."

"That black holes are massive. This is interesting to me because they seem like they would be empty thus have lower mass."

"That tidal forces would make traveling through black holes really hard to do, even if it worked because it would stretch the body, and you would probably die."

"That you can't see a black hole."

"No idea."

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

"How astronomers know how much mass objects have. This is confusing because it is not like we can ever visit these things, they just know."

"Life spans of different stars."

"The different star deaths kind of confused me, not too much, though. I just got them confused at times."

"I was a little confused on how medium mass stars die. I think I understand the process, but would greatly benefit from reviewing it."

"Death of medium mass stars."

"The picto-quiz part of the medium mass stars and how to tell which stage is which."

"The different categories of (super)nova explosions. I'm not sure how they differ and it would be nice to get some more clarification on them."

"Pulsars."

"I thought understanding the concept of black holes to be confusing. The gravitational field that surrounds black holes, the horizons, tidal forces, and gravitational redshift. I guess it wasn't really confusing because the book was pretty straightforward, but I'm just having a hard time wrapping my head around the idea of it all."

"That you can't see a black hole."

"How the Event Horizon Telescope was able to see the black hole. When will they be able to see a black hole starting to form and how will they be able to catch it the right time?"

"Nothing particularly confusing, pretty easy to follow."

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

"Because the SmartCar is more fuel efficient it uses less gas and because the Hummer H2 isn't as fuel efficient, it has a bigger gas tank to make up for its lack of efficiency."

"Because although the SmartCar has a smaller fuel tank, it also requires less fuel to run. On the other end, the Hummer requires more gas, and has a larger fuel tank to compensate for it."

"The SmartCar engine holds a smaller amount of gasoline but does a better job of efficiently using it whereas the big H2 burns up gasoline much quicker."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)

Black hole: massive main sequence star [88%]
Neutron star: massive main sequence star [38%]
White dwarf: medium-mass main-sequence star [50%]
(No stellar remnant observed yet: low-mass main-sequence star [46%]

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 [73%]
Nova: medium-mass main-sequence star [38%]
Low-mass main-sequence star: (no explosion possible) [66%]

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.	* [1]
hours.	[0]
days.	* [1]
a year.	* [1]
many years.	** [2]
forever.	****************** [18]
(Unsure/guessing/lost/help!)	*** [3]

The first rule of astronomy class is...

"Ask questions?"

"To call you P-dog?"

"Be engaged? Don't be disrespectful? Don't eat the nebulas even though they look like cotton candy?"

"Listen to P-dog if you want to be a successful human and know more about astronomy related topics and stuff?"

"I feel like I am missing something because I do not know how to answer this at all."

"Always look up?"

"Study?"

"Buy your own starwheel?"

"Go to class?"

"Do the online reading assignments? "

"To never procrastinate?"

"I honestly have no idea. Did I miss this in class?"

"You do not talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"It's funny to talk about Hummers and SmartCars because in high school I drove a SmartCar--it was embarrassing."

"Is there an actual first rule to astronomy class, or was I absent the day we went over it? "

"What is the first rule of astronomy class?"

"Will we discuss the first picture taken of the black hole?"

"What would happen after two black holes collide?" (There would be an even bigger black hole.)

Astronomy quiz question: B5 supergiant vs. K5 main sequence star

Astronomy 210 Quiz 5, spring semester 2019
Cuesta College, San Luis Obispo, CA

A B5 supergiant has a ___________ than a K5 main sequence star.
(A) brighter luminosity.
(B) larger size.
(C) hotter temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (E)

An H-R diagram is provided with this quiz.


These stars are plotted on an H-R diagram below. The B5 supergiant has a brighter luminosity, larger size, and a hotter temperature than the K5 main sequence star.


Section 30676
Exam code: quiz05S4re
(A) : 1 student
(B) : 3 students
(C) : 5 students
(D) : 7 students
(E) : 22 students
(F) : 0 students

Success level: 62% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.70

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

Astronomy 210, spring semester 2019
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.

"I find it interesting how many stars are out there and how they work. I don't understand how everything works, but it's great to know that there are people that care and share their learning with us to help us understand."

"I thought it was interesting about the weight of the layers in the sun being related to water in a swimming pool because that example helped me understand it."

"The cheerleader example for pressure and mass really helped."

"How you used cheerleaders as a representation for how more or less pressure on the core of a star produces more or less fusion and thus is brighter, or dimmer."

"The section on the star mass and luminosity relationship, because different types of stars have different relationships between mass, density, and luminosity."

"How there are only three true nebulae colors meaning there are a lot of fake pictures of space."

"I really liked reading about nebulae. I never knew there were more than one type, and apparently there are three."

"It was really cool to learn the reasons behind certain colors of nebulae. I didn't know that emission gave off a pinkish color, or that reflection was blue, but the example about cigarette smoke sometimes taking on the blue tint made sense."

"Learning more about how a star forms was quite interesting. They are such massive objects, its fascinating seeing how they started."

"Supernova shockwaves seem like an interesting subject to look into further."

"Pictures of cheerleaders. Just kidding. I really like the house party model, it's a great way to remember this! It was one of the easiest to remember models so far in class."

"I found your house party diagram very helpful in describing the different types of stars, it helps me visualize the subject better."

"Having been to lots of house parties I found the house party model to be the most interesting."

"I thought the house party analogy was very funny but also a good technique to help us remember information on the stars."

"I actually thought the house party model was helpful :P at first I was like how can this even relate to astronomy but then reading on I was like 'ohhhh.' Also, I was on Xbox as I was reading that and it just made the whole thing relatable."

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

"The H-R diagram is kinda confusing to me."

"I found the H-R diagram to be confusing to me because I'm not sure how to use it."

"I'd like a deeper explanation of fusion, it's a lot."

"Fusion was actually really confusing for me. I don't really understand it, I think the book just confused me when I tried to read it."

"I was very confused about the proton-proton chain and CNO cycles."

"Hydrostatic equilibrium was a confusing concept, just because it seemed pretty complicated, but I feel like I can understand it if I just study the GIF animation a bit more."

"Fusion rates."

"Why are the masses all over the place for the non-main sequence stars?"

"Whether a nebula emits light itself, or is it reflecting light."

Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)

Massive: brightest luminosity [90%]
Medium-mass (sunlike): medium luminosity [97%]
Low mass (red dwarf): dimmest luminosity [90%]

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 [77%]
Medium-mass (sunlike): medium fusion rate [93%]
Low mass (red dwarf): slowest fusion rate [80%]

Fusion requires high temperatures in order for nuclei to move quickly enough to:

break heavy elements apart.	***** [5]
create convection currents.	***** [5]
overcome gravity.	*** [3]
overcome repulsion.	************* [13]
(Unsure/guessing/lost/help!)	**** [4]

Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.

"Because the hydrogen nuclei are both positive so they naturally repel each other. So they need to be hot to move fast such that they overcome their repulsion. The atomic nuclei have to come at each other with enough speed and temperature to break the repulsion. An object's temperature is just a measure of the overage speed with which its particles move. A high temperature ensures that collisions, between nuclei are violent and a high density ensures that there are enough collisions, to produce enough energy to keep the sun stable. Cold fusion is implausible because there needs to be heat in order to be collisions. "

Match the three different types of nebulae with their colors.
(Only correct responses shown.)

Emission: pink [90%]
Reflection: blue [87%]
Dark: brown/black [90%]

Match the three different types of nebulae with their composition.
(Only correct responses shown.)

Emission: hydrogen [83%]
Reflection: small dust particles [83%]
Dark: large dust particles [83%]

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 [90%]
Medium-mass (sunlike): medium main-sequence lifetime [93%]
Low mass (red dwarf): longest main-sequence lifetime [83%]

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.	************************ [24]
After most everyone has left.	[0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Would it be possible to go over fusion in class? I don't really understand it."

"The textbook states that 'true stars' are powered by nuclear fusion. Is there such a thing as a 'false star?' the stars we see at night or is it a sun-like star but powered by something else?" (A "star" in general denotes something that emits light from its own energy source. The main-sequence stars (what we could consider as "true stars") fuse hydrogen in their cores to produce energy. Protostars aren't hot enough to fuse hydrogen, but they produce energy from their own gravitational contraction. Supergiants and giants produce energy from fusing stuff heavier than hydrogen.)

"I'd like a fair amount of lecture on these topics."

"Did you come up with the house party analogy yourself?" (Actually, yes.)

"The house party model was totally relatable. Thanks for that."

"What's the craziest party story you have from when you went to college?" (I don't really remember specific details. So maybe it really was a crazy party. #coolstorybro)

"What happens when a star explodes?" (We'll find out in next week's class.)

"With all the squeezing that takes place from a sun collapsing into black holes, and the pressure there being so immense, could there possibly be a new form of fusion taking place past the event horizon?" (Well, no one will every know what goes on within the event horizon.)

"If hydrogen is just one proton and no neutrons, but all protons 'hate each other,' how the heck can a molecular cloud be filled with proton-rich hydrogen, yet still 'self-start' by continually clumping together exponentially until it somehow pulls in even more stuff to create more complex structures? It just seems kinda contradictory." (Don't underestimate the power of the gravitational force. If a molecular cloud is cool enough that stuff moves slowly, and if it is large enough (light years across), then over time gravitational forces between everything will eventually pull the cloud in on itself to make a star (or planets).)

"Do you speak other languages?" (Is Hawaiian pidgin a language?)