The protosun became a full-fledged star when:
A)thermonuclear fusion reactions began at its center.
B)the temperature began to rise at its center.
C)it became hot enough to emit light and heat.
D)planetary formation was complete.

Question

Quizplus · Accepted Answer

The protosun became a full-fledged star when thermonuclear fusion reactions began at its center, causing it to emit light and heat. This is the process by which stars produce their energy and is the defining characteristic of a star. The other options may be part of the process leading up to the protosun becoming a star, but only thermonuclear fusion reactions mark the transition to a full-fledged star.

The Protosun Became a Full-Fledged Star When