You receive 8 × 10−9 W/m2 of energy from a star that is 2 parsecs away, it has a V -band apparent magnitude mV = −1.5. How much more/less flux do you receive from a star with an apparent magnitude mV = 5.3? For the first star, what is its V -band absolute magnitude?

The mass-luminosity relation describes the mathematical relationship between luminosity and mass for main sequence stars.  It describes how a star with a mass of 4 M⊙ would have a luminosity of ______ L⊙. If a star has a radius 1/2 that of the Sun and a temperature 4 that of the Sun, how many times higher is the star's luminosity than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a radius 2 times larger than the Sun's and a luminosity 1/4th that of the Sun, how many times higher is the star's temperature than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a surface temperature 2 times lower than the Sun's and a luminosity the same as the Sun, how many times larger is the star than the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125)

Wavelength = 656 nm, aperture d = 10m

If a T Tauri star is the same temperature as the Sun but is eighteen times more luminous, what is its radius relative to the Sun? (Hint: Use the luminosity-radius-temperature relation: L L  =    R R   2     T T   4   .) R R  =