# Emissive power for a gas

1. Aug 5, 2009

### lumberbunny

How does the emissive power for a gas depend on temperature? Is there a conceptual generalization (along the lines of Planck's Law) for the radiation of power from a partially transparent material or must a specific emission spectrum be chosen?

Thanks

2. Aug 5, 2009

### lumberbunny

Okay, after rereading it I notice that my original post is a little lacking in detail, so let me form it into a more concrete problem:

Say that there's a sphere of radius R surrounded by empty space but fill with gas X and at temperature T. What is the total power emitted to the surrounding space and what are the relevent properties of the gas?

I assume that any possible answer is bounded by the power emitted by a blackbody of the same size, but how is the actual power related to the properties of the gas?

Now, turning it up a notch, say there's is a finite mass M of the gas normally distributed with standard deviation S. What is the total emitted power from the mass when seen very far from the center?