Astronomy 210 Quiz 6, spring semester 2018
Cuesta College, San Luis Obispo, CA
A star cluster with medium-mass protostars would also have __________ at the same time.
(A) massive main sequence stars.
(B) red dwarfs.
(C) white dwarfs.
(D) giants.
Correct answer (highlight to unhide): (A)
All stars in a star cluster are born at the same time, but undergo stellar evolution at different rates depending on their masses. Medium-mass stars start out as protostars, then reach their main sequence stage, and subsequently become giants, planetary nebulae, and then white dwarfs. So a star cluster with medium-mass protostars cannot have giants nor white dwarfs at the same time, as these are stages that follow the protostar stage of a medium-mass star.
A red dwarf is a low-mass star that has evolved from its protostar stage to its main sequence stage; this takes much longer for a medium-mass star to evolve from its protostar stage to its main sequence lifetime. So a star cluster with medium-mass main sequence stars cannot have red dwarfs at the same time.
A massive star will evolve from its protostar stage to its main sequence stage at a rate much rapidly than medium-mass stars. Thus it is plausible that a star cluster with medium-mass protostars can have massive main sequence stars at the same time.
Section 30676
Exam code: quiz06s0ho
(A) : 17 students
(B) : 5 students
(C) : 10 students
(D) : 10 students
Success level: 44% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55
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