Online reading assignment: stellar parameters (SLO campus)

Astronomy 210, spring 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 parallax, distance, apparent magnitude, absolute magnitude, Wien's law and the Stefan-Boltzmann law.

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.
"Stars are hot, yo!"

"Its interesting that it seems like a lot of stuff in astronomy is backwards. For example, someone would want to originally consider a red thing to be hotter but no its actually blue thats hottest. And that blackbody radiation would have to do with blackness but no it actually has to do with glowing objects instead. It all seems like it's meant to trick us."

"As an art major, I found it interesting that stars follow a sort of 'reverse order' for their color to temperature relation; in art cooler colors are blue, green, purple, and warmer colors are red, orange, and yellow. Stars, however, the hottest appear white or blue in color, while the coolest appear reddish."
I'm just shocked I didn't know the order of the brightness and temperature of stars."

"I was surprised that blue stars were the hottest, assumed they were going to be much cooler than the red and orange stars."

"I think its interesting that the temperature of a star affects the color, I always figured the color depended upon the gases that made up the star."

"I found luminosity and Wien's law to be pretty interesting with the how a star's distance can be measured in its color. I don't know why, it's just always rang as pretty cool to me that we humans can judge the temperatures stars around Earth, all based in colors."
"For some reason I always thought that brown dwarf stars were really hot. But it's actually the complete opposite and I found that very interesting."

"I am not finding any of it interesting."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"How to determine the distance of stars--basically that whole thing."

"For me I found it interesting how you find the luminosity of a star based on the size and temperature, or maybe it is the size you are finding out based on the luminosity and temperature , I'm not really sure what is going exactly so some explanation here would be helpful."

"I didn't find anything particularly confusing."

"Please please pleassse go over the H-R diagram. I know it would be helpful if I could read it better."

"I don't really understand the definition of absolute visual magnitude. What I'm grasping is that it's the brightness if the star was moved to 10 parsecs (making it obvious which stars are brighter because they're all equally distant)."

"I did not find any of the information interesting because it is all confusing to me. "

"Measurements of stars? Makes me think of math and I am not good at it."

Explain how apparent magnitude and the absolute magnitude are defined differently.
"Absolute magnitude is the actual real brightness of the star. Apparent magnitude is only how bright it appears as seen from Earth."

"Apparent magnitude is how bright the star appears at its actual distance, while absolute magnitude is the brightness the star would have if it was moved to 10 pcs away."

"Apparent: what it looks like from Earth. Absolute: what it actually is."

Suppose the sun was moved to a distance of 10 parsecs away. As a result, its __________ magnitude would become dimmer.
absolute.  ******** [8]
apparent.  ************************** [26]
(Both of the above choices.)  ** [2]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  [0]

Rank the temperatures of these stars (1 = hottest, 4 = coolest; there are no ties).
(Only correct responses shown.)
Hottest: blue supergiant [97%]
Second hottest: white dwarf [78%]
Third hottest: yellow supergiant [81%]
Coolest: red dwarf [97%]

Two stars (equally far away) have the same temperature, but one star is dimmer, and the other star is brighter. The __________ star will be larger in size.
dimmer.  ** [2]
brighter.  ******************************* [31]
(These stars would be the same size.)  * [1]
(Unsure/guessing/lost/help!)  *** [3]

Two stars (equally far away) have the same brightness, but one star is cooler, and the other star is hotter. The __________ star will be larger in size.
cooler.  *************** [15]
hotter.  *************** [15]
(These stars would be the same size.)  *** [3]
(Unsure/guessing/lost/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I really enjoy the diagrams you draw on the board. I find them very helpful and resourceful. Not to mention I like copying them and making them cute in my notebook--it's a girl thing."

"Why did I not know about all the help on your blog? I feel like an idiot lol." (Duh-doy.)

"How do you feel about how well the 'flipped class' is working?" (As much as I like the format, I do have to be a scientist about it, so I'm gathering data to find out how much you are learning (versus my traditional classes from previous semesters), and will be evaluating this hypothesis eventually.)

"Will we be using the telescopes in class anymore to look at the stars and planets?" (I will try to schedule another observatory visit soon, either before class (to look at sunspots during the day) and/or after class at night (to see Jupiter, the Orion Nebula, the Pleiades, and other cool stuff.)

"How many more extra-credit opportunities will be available?" (As many as you need. At least two more this semester.)

"I tried miso soup and all I could think about was convection currents."(And how tasty it was, right? RIGHT?)

"I heard that the sun is in a binary system with another star, is this true?" (Previously, maybe. But NASA Wide-field Infrared Survey Explorer (WISE) space telescope results announced earlier this month totally debunked this.)

"Were you happy with the midterm scores?" (Meh. I could be happier. You could all make me happier on the next midterm.)

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