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 question was asked subsequent to an OBAFGKM Poetry Slam in-class activity.)
Which star is the hottest? (Graded for completion.)
(A) F5 supergiant.
(B) B0 main-sequence star.
(C) M5 main-sequence star (red dwarf).
(D) A0 white dwarf.
Student responses (pre-instruction)
Sections 70160
(A) : 5 students
(B) : 12 students
(C) : 4 students
(D) : 13 students
Correct answer: (B)
On an H-R diagram, and/or using the OBAFGKM spectral type sequence (running from hottest to coolest), B0 is the hottest start of the choices listed. (Note that the usual "I'm lost, and don't know how to answer this" response for non-exam questions was inadvertently left out of this question.)
(Students were then prompted to fill in a text box online to justify their answer.)
Briefly explain your answer, about your choice for smallest star. (Graded for completion.)
The following are all of the student responses to this question, verbatim and unedited.
"OBAFGKM"
"The hotter it gets, the brighter the light; hence white is the hottest."
"Because it has white next to it, White is one of the hottest stars"
"because on the Kelvin scale its the hottest, and B is the farthest away"
"it has the hottest temp because its white and its in the A0 quadrant."
"The main sequence is about 10,000 degress and the white dwarf is about 7,000"
"because it is blue"
"OBAFGKM, moving from hottest to coolest. B comes earliest in the sequence, as illustrated on the star chart given in class."
"B' stands for blue which is the 2nd hottest colored temp. That means the main sequence star is hotter than the rest, even the white dwarf.
eenie meanie mynee mo"
"because i'm smart and i pay attention"
"Im not quite sure"
"B0 main-sequence is higher than the other choices."
"This star has the hottest temperature and the largest luminosity on the star chart"
"according to the memorization tool you had us make up, B comes before all the other letters."
"From hottest to coolest, B-A-F-M. Main sequence star is hottest, based on it's letter (B) being second in line for hottest star, behind O."
"hey."
"The white dwarf is the hottest star because white is the hottest you can go on the spectrum."
"because its white"
"on the S and G chart b level stars are the hottest."
"i looked on the cheat sheet you gave us and using process of elimination, i chose the answer that was correct. to chose any other answer would not be correct."
"It just is."
"I don't know"
"OBAFGKM or something like that... either way, B comes before A, M, or F"
"B is closet to the left. which is the hottest."
"the one that is blue"
"White dwarf is smaller but very compacted and dense"
"O, B, A, F, G, K, M.... This sequence goes from left to right... Left is the hottest, so B0 must be the hottest since there are no O stars available! Right?"
"because B is higher surface temp than all the others except for O and on the chart the hottest is main sequence then all the other options."
091013-NCCpreOBAFGKMhttp://www.flickr.com/photos/waiferx/4023867044/
Originally uploaded by Waifer X
Wordle.net tag cloud for the pre-OBAFGKM Poetry Slam NCC section (http://www.wordle.net/show/wrdl/1240070/Untitled).
(A different section of this class was given the same online reading assignment, but was asked this question after an OBAFGKM Poetry Slam in-class activity.)
Student responses (post-instruction)
Sections 70158
(A) : 2 students
(B) : 18 students
(C) : 1 student
(D) : 8 students
"Because its between 20,000 and 30,000 in temp in the chart. Its at the farthest left."
"because its white."
"The hottest star is M5 because the temperature for stars goes..OBAFGKM."
"Its Bigger"
"because the white dwarf star is hot..."
"White = Hot"
"not really sure...this was just a guess according to figure 7-7 in Ch. 7 readings."
"A class-B star has a temperature range of about 10,000 - 30,000 degrees K, which is hotter than any of the other options."
"i guessed"
"I don't know..."
"The brighter the main sequence star is the hotter it gets. A 'B' star is the farthest left of these four on the spectrum"
"A0 is the hottest a star can get being over 10000 kelvin"
"has a greater surface temperature on the spectrum then a main sequence star."
"I am not sure."
"white is the hotest color"
"White Hot"
"white hot"
"because of the size and luminosity ratio copared to the other stars"
"On the chart we got in class, the BO main-sequence star is the hottest."
"I can hardly remember the chart, but i'm sure its the supergiants cuz they are the highest up there on the chart :P"
"according to the graph its the hottest because the sun is about 6000 kelvin and a BO mainsequence has a surface temperature of 20,000 to 50,000 kelvin"
"Color reflects temperature and white is the hottest"
"using the Hertzsprung-Russell diagram we see that A stars are hotter than B,F, and M stars. the number after the letter is simply more specific classification which is in this comparison unnecessary."
"because B stars are hotter than the others"
"The red dwarf stretches across to a temperature of 50,000 being the hottest temperature while the others fall short of that degree."
"On the star diagram the BO main sequence stars are furthest on the temperature scale."
"B0 main-sequence star is the hottest because it is blue, closest to the left."
"In the spectral sequence, B stars are hotter than all but O stars which are the hottest."
"a supergiant star is the hottest because it is the most lumionous and it has a large section in the highest tempature on the H-R diagram."
"White is hotter than red."
"Because in the sequence OBAFGKM (with O being the hottest and M the coolest), B is the closest to O in the snaswers provided."
"Thats what these notes say..."
"because white is the hottest color on the spectrum"
"The first two letters that classify the temp. of stars are O and B since there is no O star listed it would be the star in the B zone."
091014-SLOpostOBAFGKMhttp://www.flickr.com/photos/waiferx/4023867274/
Originally uploaded by Waifer X
Wordle.net tag cloud for the post-OBAFGKM Poetry Slam SLO section (http://www.wordle.net/show/wrdl/1240073/Untitled).
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