What critical event transforms a protostar into a normal main-sequence star?
A) Planets form in the accretion disk.
B) The star grows suddenly larger in radius.
C) Triple-alpha reactions begin in the core.
D) Nuclear fusion begins in the core.
E) Convection begins throughout the star's interior.

Question

Quizplus · Accepted Answer

A protostar becomes a main-sequence star when nuclear fusion begins in its core, specifically the fusion of hydrogen into helium, which provides the energy that makes the star shine.

What Critical Event Transforms a Protostar into a Normal Main-Sequence