The H-R diagram for open star clusters (See Figure 19-15 of Universe, 11th ed.) shows the Sun at approximately the 10-billion-year mark on the main sequence. What is the meaning of this?

A)The present age of the Sun is approximately 10 billion years.
B)The Sun will change its position very little on the diagram during the rest of its main sequence lifetime and thus will still be near the 10-billion-year mark when it finishes its hydrogen burning.
C)The Sun will evolve a considerable distance up the main sequence, toward higher luminosities, before it leaves the main sequence.
D)The Sun will evolve a considerable distance down the main sequence, toward lower luminosities, before it leaves the main sequence.

Question

The H-R diagram for open star clusters (See Figure 19-15 of Universe, 11th ed.) shows the Sun at approximately the 10-billion-year mark on the main sequence. What is the meaning of this?
​
 ​
A)The present age of the Sun is approximately 10 billion years. 
B)The Sun will change its position very little on the diagram during the rest of its main sequence lifetime and thus will still be near the 10-billion-year mark when it finishes its hydrogen burning. 
C)The Sun will evolve a considerable distance up the main sequence, toward higher luminosities, before it leaves the main sequence. 
D)The Sun will evolve a considerable distance down the main sequence, toward lower luminosities, before it leaves the main sequence.

Quizplus · Accepted Answer

The H-R diagram for open star clusters shows the position of stars of different ages and evolutionary stages. The fact that the Sun is located at approximately the 10-billion-year mark on the main sequence means that it is a middle-aged star, halfway through its main sequence lifetime. Since stars evolve slowly along the main sequence, the Sun will not change its position very much on the diagram during the rest of its main sequence lifetime. Therefore, it will still be near the 10-billion-year mark when it finishes its hydrogen burning.

The H-R Diagram for Open Star Clusters (See Figure 19-15