You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?
A) It emits most strongly in visible and ultraviolet light.
B) It is surrounded by a planetary nebula.
C) Every decade or so, it erupts in a nova explosion.
D) It dims and brightens more than twice per second.
Question 2
Which of the following is the best answer to the question, Why does the Sun shine?
A) The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.
B) The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.
C) 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.
D) As the Sun was forming, gravitational contraction increased the Sun's temperature until the core became hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
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