Astronomy 10, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal M3.1
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] According to the Stefan-Boltzmann law, how does the luminosity of a medium mass or massive main sequence star change as its outer layers expand and cool off, as it becomes a giant or supergiant?
(A) It becomes dimmer.
(B) It remains the same.
(C) It becomes brighter.
(D) (Any of the above (A)-(C) choices, depending on how old the star is.)
Correct answer: (B).
The evolutionary track of a main sequence star as it becomes a giant or supergiant can be approximated as a horizontal path from left-to-right across an H-R diagram, which means that its luminosity remains constant while its surface temperature decreases. From the Stefan-Boltzmann law, constant luminosity means that size must increase while temperature decreases.
Student responses
Section 4136
(A) : 13 students
(B) : 3 students
(C) : 9 students
(D) : 5 students
Section 5076
(A) : 8 students
(B) : 6 students
(C) : 4 students
(D) : 2 students
20070424
Astronomy quiz question: CNO cycle stars
Astronomy 10 Quiz 9, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.4
[3.0 points.] Which one of the following choices best explains what allows hydrogen to fuse together with much heavier elements in the cores of massive main sequence stars?
(A) Stronger gravitational forces.
(B) Stronger degenerate pressures.
(C) Continuous absorption and reemission of higher energy photons.
(D) Higher temperatures.
(E) Stronger convection currents.
Correct answer: (D)
Higher temperatures mean faster speeds. For hydrogen fusion, the temperature must be high enough for protons to approach close enough to fuse, in spite of the mutually repulsive force due to their positive charge. For hydrogen to fuse together with a heavier element (such as carbon, which has 14 protons), the temperature must be even higher for the hydrogen proton to approach the stronger repelling carbon nucleus.
Student responses
Section 4136
(A) : 18 students
(B) : 6 students
(C) : 3 students
(D) : 2 students
(E) : 10 students
Student responses
Section 5076
(A) : 5 student
(B) : 2 students
(C) : 3 students
(D) : 10 students
(E) : 1 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.4
[3.0 points.] Which one of the following choices best explains what allows hydrogen to fuse together with much heavier elements in the cores of massive main sequence stars?
(A) Stronger gravitational forces.
(B) Stronger degenerate pressures.
(C) Continuous absorption and reemission of higher energy photons.
(D) Higher temperatures.
(E) Stronger convection currents.
Correct answer: (D)
Higher temperatures mean faster speeds. For hydrogen fusion, the temperature must be high enough for protons to approach close enough to fuse, in spite of the mutually repulsive force due to their positive charge. For hydrogen to fuse together with a heavier element (such as carbon, which has 14 protons), the temperature must be even higher for the hydrogen proton to approach the stronger repelling carbon nucleus.
Student responses
Section 4136
(A) : 18 students
(B) : 6 students
(C) : 3 students
(D) : 2 students
(E) : 10 students
Student responses
Section 5076
(A) : 5 student
(B) : 2 students
(C) : 3 students
(D) : 10 students
(E) : 1 students
20070420
Bon mots: understanding trumps math
"I love only nature, and I hate mathematicians."
--Richard Feynman
"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
Upon seeing the first quote in the class announcements, a student asked who Richard Feynmann was, although it was not clear whether this interest was due to a pro-nature or anti-math sentiment.
--Richard Feynman
"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
Upon seeing the first quote in the class announcements, a student asked who Richard Feynmann was, although it was not clear whether this interest was due to a pro-nature or anti-math sentiment.
20070417
Astronomy in-class activity: OBAFGKM poetry slam, illustrated
Astronomy 10, spring semester 2007
Cuesta College, San Luis Obispo, CA
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Three favorites from this semester, by virtue of including illustrations (which were projected onto an overhead screen while the students read their poems):
Oh Because A Freaking Giraffe Kicked Me Right Near Something Critical.
--J. S.
Only Beautiful Astronomers Find Gorgeous Killer Moons.
--D. S.
Oh Bummer, Another Freaky Giant Killer Monkey Raided Nearby School Classes.
--S. P.
Previous post: OBAFGKM poetry slam (Spring Session 2007).
Plus a favorite from a past semester (Fall 2005):
Oh Beautiful Astronomical Friends Go Kiss Mr. Len.
--B. B.
Cuesta College, San Luis Obispo, CA
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Three favorites from this semester, by virtue of including illustrations (which were projected onto an overhead screen while the students read their poems):
Oh Because A Freaking Giraffe Kicked Me Right Near Something Critical.--J. S.
Only Beautiful Astronomers Find Gorgeous Killer Moons.--D. S.
Oh Bummer, Another Freaky Giant Killer Monkey Raided Nearby School Classes.--S. P.
Previous post: OBAFGKM poetry slam (Spring Session 2007).
Plus a favorite from a past semester (Fall 2005):
Oh Beautiful Astronomical Friends Go Kiss Mr. Len.--B. B.
20070416
Astronomy in-class activity: OBAFGKM poetry slam
Astronomy 10, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Two favorites from this semester:
Oops! Britney Attacked Federline's GMC. Kevin's Mad.
--C. K.
Only Batman Always Forgets Giant Kryptonite Meteorites Resting Near Superman's Car.
--K. P.
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.
Two favorites from this semester:
Oops! Britney Attacked Federline's GMC. Kevin's Mad.
--C. K.
Only Batman Always Forgets Giant Kryptonite Meteorites Resting Near Superman's Car.
--K. P.
20070413
Astronomy clicker question: protostar to main sequence evolution
Astronomy 10, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] How is it possible for the luminosity of a protostar to remain (approximately) constant as it becomes a main sequence star?
(A) Its surface temperature gets hotter as its size gets smaller.
(B) Its surface temperature gets cooler as its size gets smaller.
(C) Its surface temperature gets hotter as its size gets larger.
(D) Its surface temperature gets cooler as its size gets larger.
Correct answer: (A).
The evolutionary track of a protostar as it becomes a main sequence star can be approximated as a horizontal path from right-to-left across an H-R diagram, which means that its luminosity remains constant while its surface temperature increases. From the Stefan-Boltzmann law, constant luminosity means that size must decrease while temperature increases.
Student responses
Section 4136
(A) : 19 students
(B) : 2 students
(C) : 7 students
(D) : 1 student
Student responses
Section 5076
(A) : 7 students
(B) : 0 students
(C) : 13 students
(D) : 1 student
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
[0.3 points.] How is it possible for the luminosity of a protostar to remain (approximately) constant as it becomes a main sequence star?
(A) Its surface temperature gets hotter as its size gets smaller.
(B) Its surface temperature gets cooler as its size gets smaller.
(C) Its surface temperature gets hotter as its size gets larger.
(D) Its surface temperature gets cooler as its size gets larger.
Correct answer: (A).
The evolutionary track of a protostar as it becomes a main sequence star can be approximated as a horizontal path from right-to-left across an H-R diagram, which means that its luminosity remains constant while its surface temperature increases. From the Stefan-Boltzmann law, constant luminosity means that size must decrease while temperature increases.
Student responses
Section 4136
(A) : 19 students
(B) : 2 students
(C) : 7 students
(D) : 1 student
Student responses
Section 5076
(A) : 7 students
(B) : 0 students
(C) : 13 students
(D) : 1 student
20070411
Astronomy quiz question: applications of the Stefan-Boltzmann law
Astronomy 10 Quiz 8, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[Version 1]
[3.0 points.] Which one of the following statements best describes the relationship between a main sequence star and a supergiant that have the same luminosity?
(A) The main sequence star is cooler and smaller than the supergiant.
(B) The main sequence star is cooler and larger than the supergiant.
(C) The main sequence star is hotter and smaller than the supergiant.
(D) The main sequence star is hotter and larger than the supergiant.
(E) (None of the above choices (A)-(D), as it is not possible for a main sequence star to have the same luminosity as a supergiant.)
Correct answer: (C)
From an H-R diagram, a main sequence star must be hotter in order to have the same luminosity as a supergiant. From the Stefan-Boltzmann law, since luminosity is proportional to size and temperature^4, and with both stars having the same luminosity, the hotter star must be smaller in size.
Student responses
Section 4136
(A) : 6 students
(B) : 3 students
(C) : 22 students
(D) : 1 student
(E) : 0 students
[Version 2]
[3.0 points.] Which one of the following statements best describes the relationship between a main sequence star and a white dwarf that have the same luminosity?
(A) The main sequence star is cooler and smaller than the white dwarf.
(B) The main sequence star is cooler and larger than the white dwarf.
(C) The main sequence star is hotter and smaller than the white dwarf.
(D) The main sequence star is hotter and larger than the white dwarf.
(E) (None of the above choices (A)-(D), as it is not possible for a main sequence star to have the same luminosity as a white dwarf.)
Correct answer: (B)
From an H-R diagram, a main sequence star must be cooler in order to have the same luminosity as a supergiant. From the Stefan-Boltzmann law, since luminosity is proportional to size and temperature^4, and with both stars having the same luminosity, the cooler star must be larger in size.
Student responses
Section 5076
(A) : 3 students
(B) : 10 students
(C) : 1 student
(D) : 4 students
(E) : 2 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
[Version 1]
[3.0 points.] Which one of the following statements best describes the relationship between a main sequence star and a supergiant that have the same luminosity?
(A) The main sequence star is cooler and smaller than the supergiant.
(B) The main sequence star is cooler and larger than the supergiant.
(C) The main sequence star is hotter and smaller than the supergiant.
(D) The main sequence star is hotter and larger than the supergiant.
(E) (None of the above choices (A)-(D), as it is not possible for a main sequence star to have the same luminosity as a supergiant.)
Correct answer: (C)
From an H-R diagram, a main sequence star must be hotter in order to have the same luminosity as a supergiant. From the Stefan-Boltzmann law, since luminosity is proportional to size and temperature^4, and with both stars having the same luminosity, the hotter star must be smaller in size.
Student responses
Section 4136
(A) : 6 students
(B) : 3 students
(C) : 22 students
(D) : 1 student
(E) : 0 students
[Version 2]
[3.0 points.] Which one of the following statements best describes the relationship between a main sequence star and a white dwarf that have the same luminosity?
(A) The main sequence star is cooler and smaller than the white dwarf.
(B) The main sequence star is cooler and larger than the white dwarf.
(C) The main sequence star is hotter and smaller than the white dwarf.
(D) The main sequence star is hotter and larger than the white dwarf.
(E) (None of the above choices (A)-(D), as it is not possible for a main sequence star to have the same luminosity as a white dwarf.)
Correct answer: (B)
From an H-R diagram, a main sequence star must be cooler in order to have the same luminosity as a supergiant. From the Stefan-Boltzmann law, since luminosity is proportional to size and temperature^4, and with both stars having the same luminosity, the cooler star must be larger in size.
Student responses
Section 5076
(A) : 3 students
(B) : 10 students
(C) : 1 student
(D) : 4 students
(E) : 2 students
20070410
Astronomy clicker question: why are white dwarfs small?
Astronomy 10, Spring Semester 2007
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the beginning of their learning cycle:
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: (A).
The fact that both stars have the same white-hot color tells you that they must have the same temperature (Wien's law). From the Stefan-Boltzmann law, luminosity is proportional to size and temperature^4, thus with both stars having the same temperature, the less luminous star is the smaller star.
Student responses
Section 4136
(A) : 9 students
(B) : 4 students
(C) : 7 students
(D) : 11 students
Section 5076
(A) : 2 students
(B) : 1 student
(C) : 10 students
(D) : 3 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q8.5
Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the beginning of their learning cycle:
[0.3 points.] Why is a white dwarf star smaller than a main-sequence star that has the same white-hot color?
(A) It is less luminous than the main-sequence star.
(B) It is more luminous than the main-sequence star.
(C) It is cooler than the main-sequence star.
(D) It is hotter than the main-sequence star.
Correct answer: (A).
The fact that both stars have the same white-hot color tells you that they must have the same temperature (Wien's law). From the Stefan-Boltzmann law, luminosity is proportional to size and temperature^4, thus with both stars having the same temperature, the less luminous star is the smaller star.
Student responses
Section 4136
(A) : 9 students
(B) : 4 students
(C) : 7 students
(D) : 11 students
Section 5076
(A) : 2 students
(B) : 1 student
(C) : 10 students
(D) : 3 students
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