# Some Astronomy/Cosmology Questions

#### stardrop

I hope this is the right place to post this! I think so. I'd really be grateful if anyone can give me any information about this--especially help with the math involved.

1. The problem statement, all variables and given/known data
How to calculate the temperature of a star using--

2. Relevant equations

λmax = Å

3. The attempt at a solution
Absolutely none, I'm completely lost. I'd really like to understand the concept, but I don't know where to begin at all!

#### OlderDan

Homework Helper
I hope this is the right place to post this! I think so. I'd really be grateful if anyone can give me any information about this--especially help with the math involved.

1. The problem statement, all variables and given/known data
How to calculate the temperature of a star using--

2. Relevant equations

λmax = Å

3. The attempt at a solution
Absolutely none, I'm completely lost. I'd really like to understand the concept, but I don't know where to begin at all!

What does this mean?

"How to calculate the temperature of a star using--"

And what does this mean?

λmax = Å

Are you saying the maximum wavelength emitted by the star is one angstrom? I seriously doubt that. If you know something about the wavelength that has the highest intensity, then the problem can be solved.

#### stardrop

I meant how do you calculate the temperature of a star using λmax = Å. This is what my teacher wrote down on the board but he didn't explain it any further. I think maybe what he wrote means what equation do you use if the information you have is λmax IN Å, but I'm not sure. That's only what would make sense to me, a complete beginner.

"If you know something about the wavelength that has the highest intensity, then the problem can be solved." Can you tell me where I can find out more about this?

Thanks for your help!

#### Max Eilerson

I assume it means λmax = 1 Angstrom = 0.1nm. If you're just given a wavelength you can only use wien's displacement law.

#### stardrop

Thanks so much! That's the answer I was looking for; now I'll read more about Wien's Displacement Law.

#### OlderDan

Homework Helper
I meant how do you calculate the temperature of a star using λmax = Å. This is what my teacher wrote down on the board but he didn't explain it any further. I think maybe what he wrote means what equation do you use if the information you have is λmax IN Å, but I'm not sure. That's only what would make sense to me, a complete beginner.

"If you know something about the wavelength that has the highest intensity, then the problem can be solved." Can you tell me where I can find out more about this?

Thanks for your help!
Max has given you the right direction. You can find more about it here

http://hyperphysics.phy-astr.gsu.edu/Hbase/wien.html#c2

The site uses λpeak rather than λmax, which is a much better description of the wavelength of interest. There is no maximum wavelength, but there is a wavelength that corresponds to the maximum in the intensity or power density curve.

#### stardrop

Thank you! Thanks for the extended explanation and the link--both were very helpful! (:

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