Astronomy quiz question: nucleosynthesis of Earth's gold and silver

Astronomy 210 Quiz 7, spring semester 2014
Cuesta College, San Luis Obispo, CA

Fusion reactions in a type Ia supernova or type II supernova produced the:
(A) helium in the sun's core.
(B) gold and silver in Earth's crust.
(C) heat inside Earth's core.
(D) lithium in car batteries.
(E) (More than one of the above choices.)
(F) (None of the above choices.)

Correct answer (highlight to unhide): (B)

Hydrogen is merely the raw ingredient of the universe. Light nuclides such as deuterium, helium and lithium are produced by fusion of hydrogen in the cores of main sequence stars, but deuterium and lithium are typically broken apart by the high pressures and temperatures there, such that stars cannot have produced any of the deuterium and lithium present in the universe today. These light nuclides were also produced by similar conditions in the first few minutes after the start of the big bang, but as the universe expanded and cooled, deuterium and lithium that would have been broken apart were preserved and these "fossil" nuclides remain to this day.

The helium in the core of the sun is produced primarily from the fusion of hydrogen during its main-sequence lifetime (with a small percentage of this helium produced during the nucleosynthesis phase of the early universe).

Stars fuse hydrogen into heavier elements in their cores. Medium-mass stars have carbon as their end product of fusion; while massive stars have iron has their end product. However, type Ia supernova of these medium-mass stars as white dwarfs would result in heavier elements than carbon being made, and especially the type II supernova of massive stars would result in much heavier elements than iron, such as gold and silver. These heavy elements from a previous generation star's remnants would then be incorporated into the formation of Earth in the early solar system.

The heat in Earth's core was produced from the conversion of gravitational potential energy during its formation, and also from the radioactive decay of unstable heavy elements in its core.

Section 30674
Exam code: quiz07nU7e
(A) : 0 students
(B) : 7 students
(C) : 0 students
(D) : 1 student
(E) : 14 students
(F) : 4 students

Success level: 32% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

Section 30676
Exam code: quiz07s1Rp
(A) : 7 students
(B) : 4 students
(C) : 1 student
(D) : 0 students
(E) : 21 students
(F) : 1 student

Success level: 19% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.10

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