1- the star Altair has its wavelength of maximum energy intensity located at about .0000004 meters. what is the temperature of Altair ? what is

1- the star Altair has its wavelength of maximum energy intensity located at about .0000004 meters. what is the temperature of Altair ? what is Altair's spectral type?

2- if the sun doubled its temperature , how much larger (or smaller) would the sun's radius have to be in order to maintain the same luminosity that it now has?

3- the crab nebula pulsar has a radius equal to .0001 that of the sun. if the temperature of the pulsar is three times that of the sun, find the luminosity of crab nebula pulsar in terms of the sun's luminosity.