USAAAO — 2025 First Round

Which of the following statements are true about a cluster of main sequence stars: A: For two star clusters of the same total mass, the one with the larger number of stars will be brighter as measured by luminosity per unit mass. B: The main-sequence turnoff point for star clusters is at higher temperatures if they are older. C: The main-sequence turnoff point for star clusters is at lower luminosities if they are older. Assume the mass-luminosity relationship L ∝ M^3.5 for main-sequence stars.