# Find the temperature and total radiancy of star

1. Oct 26, 2004

### stunner5000pt

Thank you in advance for your help!!

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

https://www.physicsforums.com/showthread.php?t=49868

4. Oct 27, 2004

### Tide

What I mean is that according to the forum rules you should indicate what work you've done so far on the problems for which you are seeking help. People are more than willing to help out if you give some indication of the effort you've made at solving a problem before you post it here but they reluctant to provide outright solutions when problems are posted with no work shown. It's not a homework service!

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