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Astronomy clicker question: type II supernova energy source

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M3.4

Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:

[0.3 points.] A supergiant will eventually explode as a type II supernova. What provides the energy for this explosion?
(A) Radioactive decays of unstable heavy elements.
(B) Fusion of light elements into heavy elements.
(C) Sudden gravitational contraction.
(D) Dark energy.

Correct answer: (C)

Student responses
Section 4160
(A) : 5 students
(B) : 9 students
(C) : 13 students
(D) : 3 students

Section 5166
(A) : 7 students
(B) : 16 students
(C) : 25 students
(D) : 6 students

Response (D) is merely a ruse (as it had not yet been covered yet in this course sequence). Response (A) is fission, which is not a source of energy for a star. Response (D) is fusion, which can no longer provide energy for a star at the end of its supergiant phase, as it core is iron at this point, past which requires more energy to be put in than can be released by fusion. Thus with no energy source to balance gravity, the core undergoes runaway contraction (becoming a neutron star in the process), and the resulting energy from this gravitational collapse of the core is transferred to the outer layers of the supergiant in an "implosion-explosion" sequence--a type II supernova.

Previous post: Type II supernova simulators.

2 comments:

Tim Fahlberg said...

Thank you for providing such an extraordinary resource through your blog of questions, etc!

Question: Do you or other professors ever use (or have you considered using) a response of "? - I don't want to guess."

I used this response frequently for formative assessment questions when I taught math at the college level and integrated the use of clickers in my teaching. Students were quite willing to choose this response because they weren't embarrassed after choosing it.

By providing this response for questions used in formative assessment I was able to get better data to inform my instruction. Sometimes (much to my chagrin) 30-50% of my students would choose this response following instruction on a topic so that I then knew I should reteach the topic and then reassess.

Your thoughts on this?

Thanks.

Tim Fahlberg

Patrick M. Len said...

Great comment--see the posting Education research: "guessing/don't know" clicker response for more comments on this topic!