1) Which of these stars will spend the shortest time on the main sequence?
The star that will spend the shortest time on the main sequence is Mintaka, which has a B-index of -0.40. This means that it is a very hot and blue star, with a spectral type of O9 V. This indicates that it has a high mass and luminosity, and therefore a short main sequence lifetime34
2) Which will spend the longest time on the main sequence?
The star that will spend the longest time on the main sequence is Bernard’s Star, which has a B-index of 1.73. This means that it is a very cool and red star, with a spectral type of M4 V. This indicates that it has a low mass and luminosity, and therefore a long main sequence lifetime34
3) Which star is brighter in the visual filter than they are in the blue?
The star that is brighter in the visual filter than they are in the blue is Bernard’s Star, which has a positive B-index of 1.73. This means that its magnitude in the blue filter is larger (and therefore dimmer) than its magnitude in the visual filter. This is because it emits most of its light at red wavelengths, which are not detected by the blue filter
4)The relationship between the color index of a star and its main sequence lifetime is inverse.