Final answer:
The evolutionary track for a significantly more massive star than the Sun would begin at a much higher luminosity and temperature on the H-R diagram, because massive stars burn their fuel faster and have shorter lifespans. This results in a rapid progression through the evolutionary stages and requires fewer years to reach the giant phase compared to Sun-like stars.
Step-by-step explanation:
The character of the evolutionary track for a more massive star on the Hertzsprung-Russell (H-R) diagram varies significantly compared to a Sun-like star. If we look at the computed tracks based on models provided, for example, by University of Illinois astronomer Icko Iben, we see each star begins its life on the zero-age main sequence, represented by the red line on the H-R diagram.
For a significantly more massive star than our Sun—like Betelgeuse with a mass about 15 times that of the Sun—the starting point on this track would be at a much higher luminosity and temperature than that of a Sun-like star. This is due to the fact that more massive stars burn their nuclear fuel at a much faster rate, leading to a shorter lifespan and rapid progression through the evolutionary stages—leaving the main sequence, becoming supergiants, and ultimately ending their lives in spectacular explosions such as supernovae.
Furthermore, the timeline for a massive star to evolve from the main sequence to the giant phase is significantly shorter than that of stars with masses closer to that of the Sun, which is illustrated in Figure 22.5 with numbers indicating the years needed to reach the giant stage.