Generally speaking, how does the surface temperature and luminosity of a protostar compare to the surface temperature and luminosity of the main- sequence star it becomes?
A)A main- sequence star is hotter and brighter than it was as a protostar.
B)A main- sequence star is cooler and brighter than it was as a protostar.
C)A main- sequence star is hotter and dimmer than it was as a protostar.
D)A main- sequence star is cooler and dimmer than it was as a protostar.

Question

Quizplus · Accepted Answer

As a protostar, the surface temperature and luminosity are higher due to the heat generated by gravitational contraction. Once nuclear fusion begins in the core, a main-sequence star becomes more stable and therefore its surface temperature and luminosity decrease. However, the star also becomes more massive and larger in size during this period.

Generally Speaking, How Does the Surface Temperature and Luminosity of a Protostar