A star on the main sequence is fusing Hydrogen in its core.?

Question

A star on the main sequence is fusing Hydrogen in its core.

A)Only true for A stars.
B)Only true for white dwarf
C)True
D)Only true for red giants.

Answer 1

True

Answer 2

A really basic question. Eliminate (D) because red giants are, by definition, not on the main sequence. Eliminate (B) because white dwarfs are remnants of stars that went off the main sequence long ago and blew off their outer layers (our Sun's fate several billion years from now).



Now the difference between (A) and (C) is just how broad the claim is. "A stars" refers to one color classification of stars, part of the color sequence OBAFGKM. Our Sun is a G star, while really hot/bright stars are O and B stars, and small dim stars (the vast majority as far as we have measured) are K amd M. *All* these colors can represent main sequence stars, and *all* main sequence stars are fusing hydrogen, so the answer is (C).



There are a ton more details around why the main sequence is called that, differences in details of hydrogen fusion based on stellar class, length of time on the main sequence, and fate of stars when they leave the main sequence. If you really did not understand intuitively the answer to the question above, you don't understand basic stellar evolution, and should go back and study it some more.



Good luck!

Answer 3

True!