Question

Each item following is a characteristic of a one-solar-mass star either during its protostar phase or during its main-sequence phase. Match the items to the appropriate phase.

-energy generated by nuclear fusion-lasts about 10 billion years
-energy generated by gravitational contraction
-radius much larger than the Sun
-pressure and gravity are Not precisely balanced
-luminosity much greater than the Sun
-surface radiated energy at same rate that core generates energy

Answer 1

Protostar phase:

-energy generated by gravitational contraction

-radius much larger than the Sun

-pressure and gravity are Not precisely balanced

-luminosity much greater than the Sun

Main-sequence phase:

-energy generated by nuclear fusion

-lasts about 10 billion years

-surface radiated energy at same rate that core generates energy

Step-by-step explanation:

There´re four stages in the formation of a one-solar-mass star:

molecular-cloud fragment, contracting cloud trapping infrared light, protostar with jets, and main-sequence star.

During the period from Protostar to Main Sequence, the surrounding gas blows away. The energy is generated by gravitational contraction rather than fusion. Contraction continues till the core is hot enough for nuclear fusion, and it stops when there´s a balance between the energy from core fusion and the one coming from the surface, turning the star into a main-sequence star.