Author Question: When does a star become a main-sequence star? A) when the protostar assembles from a molecular ... (Read 129 times)

cdr_15 · **on:** Jul 27, 2018

When does a star become a main-sequence star?

A) when the protostar assembles from a molecular cloud
B) the instant when hydrogen fusion first begins in the star's core
C) when the rate of hydrogen fusion within the star's core is high enough to maintain gravitational equilibrium
D) when a star becomes luminous enough to emit thermal radiation
E) when hydrogen fusion is occurring throughout a star's interior

Question 2

The temperature of the layer of gas that produces the visible light of the Sun is

A) 3,500 K
B) 5,800 K
C) 12,300 K
D) 300,000 K
E) 15 million K