Online reading assignment question: main-sequence lifetimes

Astronomy 210, Fall Semester 2009
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 before an in-class activity on the evolution of and main-sequence lifetimes of different mass stars.)

_________ stars have the shortest main-sequence lifetime. (Graded for completion.)
(A) Massive.
(B) Medium-mass.
(C) Low-mass.
(D) (There is a tie.)
(E) (I'm lost, and don't know how to answer this.)

Student responses (pre-instruction)
Sections 70160
(A) : 21 students
(B) : 0 students
(C) : 11 students
(D) : 0 students
(E) : 0 students

Correct answer: (A)

A massive star has the shortest main-sequence lifetime (typically less than few millions of years, compared to tens of billions of years for the low-mass main sequence stars).

(The same question above was asked of students in a different section, following an in-class activity on the evolution of and main-sequence lifetimes of different mass stars.)

Student responses (post-instruction)
Sections 70158
(A) : 29 students
(B) : 1 student
(C) : 4 students
(D) : 0 students
(E) : 5 students