Astronomy quiz question: low-mass star fusion rates

Astronomy 210 Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA

A low-mass main-sequence star will have a slow fusion rate because of the ____________ pressure and ____________ temperature in its core.
(A) low; low.
(B) low; high.
(C) high; low.
(D) high; high.

Correct answer (highlight to unhide): (A)

The rate of fusion in a star depends on the temperature (which affects the speed of hydrogen nuclei that will need to collide with enough speed to actually come into contact and fuse) and the pressure (which affects the frequency of these collisions). Since a low-mass star does not have a lot of mass, there will be not much gravitational forces squeezing its core, and these stars also have the lowest temperatures of all the main-sequence stars.

Section 70158
Exam code: quiz06SuRr
(A) : 27 students
(B) : 8 students
(C) : 7 students
(D) : 6 students

Success level: 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60

Section 70160
Exam code: quiz06N3sT
(A) : 16 students
(B) : 4 students
(C) : 4 students
(D) : 2 students

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38