Question

At what stage in its life does a star pass through the protostar phase?

A) while it is converting hydrogen into helium in its core
B) when it is expanding in size as a red giant or supergiant
C) after nuclear reactions end in its core but before the red giant phase
D) after condensation but before nuclear reactions begin in its core

Answer 1

The protostar phase occurs after condensation but before nuclear reactions begin in the star's core.

Step-by-step explanation:

The protostar phase of a star occurs during Option D) after condensation but before nuclear reactions begin in its core. This phase begins when a molecular cloud collapses under gravity, causing the gas and dust to condense and form a protostar. At this stage, the protostar has not yet begun nuclear fusion in its core.