In the H-R diagram in Figure 19-15 of Universe, 11th ed., the brightest stars in the Pleiades cluster are not on the main sequence but toward the upper right. Why is this?

A)These stars have not yet reached the main sequence and are in the T Tauri phase.
B)These stars have already evolved through the red giant phase, returned to the blue giant phase and are on their way to the white dwarf phase.
C)These stars have already become white dwarf stars, as shown by their position.
D)These blue supergiant stars have already begun to evolve toward the red supergiant phase.

Question

In the H-R diagram in Figure 19-15 of Universe, 11th ed., the brightest stars in the Pleiades cluster are not on the main sequence but toward the upper right. Why is this?
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 ​
A)These stars have not yet reached the main sequence and are in the T Tauri phase. 
B)These stars have already evolved through the red giant phase, returned to the blue giant phase and are on their way to the white dwarf phase. 
C)These stars have already become white dwarf stars, as shown by their position. 
D)These blue supergiant stars have already begun to evolve toward the red supergiant phase.

Quizplus · Accepted Answer

The Answer of In the H-R diagram in Figure 19-15 of Universe, 11th ed., the brightest stars in the Pleiades cluster are not on the main sequence but toward the upper right. Why is this?
​
 ​
A)These stars have not yet reached the main sequence and are in the T Tauri phase. 
B)These stars have already evolved through the red giant phase, returned to the blue giant phase and are on their way to the white dwarf phase. 
C)These stars have already become white dwarf stars, as shown by their position. 
D)These blue supergiant stars have already begun to evolve toward the red supergiant phase.

In the H-R Diagram in Figure 19-15 of Universe, 11th