Part A: The B-V Color Index and Lifetime of a Star on the Main Sequence Hot stars are bluer and cool redder. The B-V Color Index (B-V) is used to view stars in the blue wavelengths, and V for visual colors of yellow green by using filters. The hottest stars have a B- V close to −0.5 or less, while the coolest stars have a B-V of close to 2.0. Hottest stars do not have as long a lifetime as cool stars. Stars located on the upper part of the main sequence do not live long compared to the lower portion stars. Stars located in the upper portion of the main sequence on the H-R diagram are large, luminous, and blue that evolve through a star's life cycle quickly as it burns hydrogen to fuel the large star in a rapid manner. Given the following B-V index for the following stars, you can answer questions in Part A. 1. Which of these stars will spend the shortest time on the main sequence? 2. Which will spend the longest time on the main sequence? 3. Which star is brighter in the visual filter than they are in the blue? 4. What is the relationship between the color index of a star and its main sequence lifetime?