The Sun has nearly the same temperature today that it had 4.5 billion years ago, but it is now 30% more luminous. Why?
A) The Sun has a stronger magnetic field today.
B) The Sun has a larger surface area today.
C) The Sun has more sunspots today.
D) Energy took longer to escape the young Sun.

Question

Quizplus · Accepted Answer

The Sun's luminosity has increased because it has expanded over time, leading to a larger surface area from which more energy is emitted, even though its surface temperature has remained relatively constant.

The Sun Has Nearly the Same Temperature Today That It