Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q9.5
[Version 1]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the least amount of time? (A) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a low mass protostar as it becomes a main sequence star.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the least amount of time.)
Correct answer: (A)
Due to their greater gravitational forces, massive protostars take a relatively short amount of time to contract and heat up to initiate fusion; and also their rapid fusion rates will cause them to have a relatively short main sequence lifetime (cf. previous post on main sequence lifetimes). In contrast, medium-mass stars will take longer than that just to get from the protostar to the main sequence stages, while low-mass stars take a even longer amount of time.
Student responses
Section 4160
(A) : 25 students
(B) : 3 students
(C) : 7 students
(D) : 0 students
(E) : 0 students
[Version 2]
[3.0 points.] Shown at right is an H-R diagram of the evolutionary tracks of stars of different masses. Which one of the following choices best describes the evolutionary track that takes the most amount of time? (A) The track taken by a low mass protostar as it becomes a main sequence star.
(B) The track taken by a medium mass protostar as it becomes a main sequence star.
(C) The track taken by a massive protostar as it becomes a main sequence star, and then later becomes a supergiant.
(D) (All of the above tracks (A)-(C) take the same amount of time.)
(E) (Not enough information is given to determine which of these evolutionary tracks takes the most amount of time.)
Correct answer: (A)
Section 5166
(A) : 34 students
(B) : 2 students
(C) : 11 students
(D) : 5 students
(E) : 3 students
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