Physics Problems: Help Please!!! 1.) If a star has a temperature only 7/10 that of our Sun but a radius 10 times our Sun's, how would its luminosity compare to our Sun? The only equation I have for luminosity involves mass and apparent magnitude, so I'm not really sure what to do here. 2.) If a star has a mass 11 times our Sun's mass, what would be its lifetime on the main sequence? What if the mass were 0.09 that of our Sun? Do I use the lumionisty equation here which includes mass which is: L = M^3.5 3.) If the parallax for a star is 0.015 arc sec (as measured by the Hipparchus satellite) how far away is it in parsec? In Light Years? If it has an absolute magnitude of 3, how bright would it appear from Earth? d = 1/P to find parsecs? and then convert to light years. I'm not sure about the absolute magnitude though. 4.) If the temperature of a star is 7800 K, where is the peak wavelength from Wien's Law? Assuming that it is a Main Sequence star, what spectral class and absolute magnitude would it have? Use Wien's Law to saolve for the peak wavelength seeing as I have the temperautre. How then would I find the absolute magnitude? 5.) If a star has an Absolute Magnitude 50 times brighter than our Sun, what would it be? If it appears as a 5 magnitude star, how far away is it? No idea here. I don't have an equation or notes on this i.e. absolute magnitude.