# Homework Help: Find the temperature and total radiancy of star

1. Oct 26, 2004

### stunner5000pt

Stars act like perfect blackbodies. Star A has a surface temperature of 10^12 K. For another star B the wavelength at which the spectral radiancy is a maximum $$(\lambda_{max})^B$$ is half taht of star A.

a) Find the temperature and total radiancy of star B.(per sq m)

Using Wien's formula
Lambda T = constant

Lambda(A) T(A) = 2 Lambda (B) T(A) = Lambda(B) = T(B)
So the temperature of B is twice that of A

Also since w = 2898micormetres K then i can find out lambda.

C) A spaceship is positioned on the straight line betwen the stars A and B. The spaceship is at rest with respect to star A. Stars A and B have relative velocities such that the spectral radiancy from B appears to be 1/3 rd its wavelength. What is the relative velocity of th stars?

If the wavelength is smaller than B must be approching A(yes?) then the doppler shift formula iwth the + on top would be used.

2. Oct 27, 2004

### Tide

What have you done so far on any of these problems?

3. Oct 27, 2004

### stunner5000pt

what do you mean ?

By the way i'm fine i understand this problem quite well, i would appreciate your help with this one