Which of the following is the best answer to the question, "Why does the Sun shine?"
A) As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
B) As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.
C) The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.
D) The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.

Question

Quizplus · Accepted Answer

As per current understanding of astrophysics, the gravitational contraction of the early Sun caused the core temperature to reach a point where hydrogen nuclei could fuse into helium, releasing tremendous amounts of energy in the process. This process of nuclear fusion has been providing the energy that makes the Sun shine ever since.

Which of the Following Is the Best Answer to the Question