luminosity

[vegawoman]

Hey, I don't understand something.

How much would luminosity increase if a star's temperature and radius doubled? I'm not really sure how to figure this out or calculate it.

[mstarry]

I'm not sure but I think it would increase 4x or 16x

[qwerty mob]

Use the Stefan-Boltzmann Law; the relationship between luminosity (L) expressed in Watts (w), radius (r) expressed in Metres (m), and temperature (t) expressed in degress Kelvin (K), as a formula (forgive the format, message boards don't do subscripts or exponents very well):



L = (7.125 x 10^-7) r^2 t^4

Edit: note, (7.125 x 10^-7) = 4'pi' x 'sigma'

[vegawoman]

Thanks for all your help but I just don't get it, well I do but it just isn't working on my calculator. I'm not sure how to punch it in.

Can anyone give me an actual example with a real star or something?
i'm not sure if I am putting it in right into the calculator.

Thanks

[Facial]

If both radius and temperature doubled, then it's just a matter of math.

T^4, factor is 16
R^2, factor is 4

The luminosity should increase by 64 times.