Final answer:
Main sequence stars are plotted on the H-R diagram from the upper left (hot and luminous) to the lower right (cool and less luminous). Higher mass main-sequence stars are hotter and more luminous and thus are found in the upper left of the H-R diagram. As stars expend their hydrogen fuel, they evolve away from the main sequence, with higher-mass stars becoming red giants located in the upper right.
Step-by-step explanation:
Student two is correct when discussing main sequence stars on the Hertzsprung-Russell (H-R) diagram. Higher mass, main-sequence stars are indeed located in the upper left of the H-R diagram. This location correlates with them being hotter and more luminous than lower mass, main-sequence stars, which lie toward the cooler and less luminous lower right of the main sequence. The H-R diagram plots stars according to their luminosity and temperature, and most stars, about 90%, fall along the main sequence. These main-sequence stars derive their energy from the nuclear fusion of hydrogen into helium in their cores.
The relative position of a star on the main sequence provides information about its mass, with higher-mass stars positioned toward the hotter and more luminous end of the sequence. When main sequence stars exhaust their hydrogen fuel, they leave the main sequence. For higher-mass stars, this evolution happens quickly, and they move towards the red giant phase which is characterized by their placement in the upper right section of the H-R diagram. Over time, as star clusters age, the main-sequence turnoff point moves downward, indicating that stars of lower and lower masses are evolving away from the main sequence.