You discover a binary star system in which one member is a 15MSᵤn main-sequence star and the other star is a 10MSᵤn giant.Why should you be surprised,at least at first?
A)It doesn't make sense to find a giant in a binary star system.
B)The odds of ever finding two such massive stars in the same binary system are so small as to make it inconceivable that such a system could be discovered.
C)The two stars in a binary system should both be at the same point in stellar evolution;that is,they should either both be main-sequence stars or both be giants.
D)The two stars should be the same age,so the more massive one should have become a giant first.
E)A star with a mass of 15MSᵤn is too big to be a main-sequence star.

Question

Quizplus · Accepted Answer

The more massive a star, the faster it burns through its nuclear fuel and evolves off the main sequence. Therefore, in a binary system with a 15MSᵤn main-sequence star and a 10MSᵤn giant, it is surprising because the more massive star (15MSᵤn) should have evolved into a giant phase before the less massive one (10MSᵤn), assuming they formed at the same time.

You Discover a Binary Star System in Which One Member