Question

The source of a protostar's heat is

A) gravitational energy released as the protostar expands.
B) nuclear reactions converting helium to carbon and oxygen in its core.
C) gravitational energy released as the star contracts.
D) nuclear reactions converting hydrogen into helium in its core.

Answer 1

The source of a protostar's heat is gravitational energy released as the star contracts.

Step-by-step explanation:

The source of a protostar's heat is gravitational energy released as the star contracts. Initially, a protostar remains fairly cool with a very large radius and a very low density. As the protostar collapses under its own gravity, its surface area gets smaller, and heat is generated due to the release of gravitational potential energy. This heat is trapped inside the protostar, causing it to become denser and opaque. Therefore, option C) gravitational energy released as the star contracts is the correct answer.