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Find an equation or law within the black body bubble. Learn what you need for the equation to work. Try out an example using the equation found. I first found the black body radiation in Wikipedia and other sources and found that a key component is the **Planck's Law**. What is requires is: the Planck's Constant, speed of light, Boltzmann Constant, the frequency of electromagnetic radiation, the temperature in Kelvins, and the amount of energy per unit surface area per unit time per unit solid angle emitted in the frequency range between //ν// and //ν// + //dν// by a black body at temperature //T//.
 * Background:** In the universe there are galaxies. In these galaxies there are millions and even a trillion stars in them. As humans and as scientists we like to categorize things by their distinct features. We already have a way of differentiating different galaxies from their spectra but is there another correlation between them? Maybe we can use the average temperature of a galaxy to determine what kind it is as well as how old it is.
 * Question:** How you would estimate the average temperature of a star in a galaxy, from the galaxy's spectrum?
 * Ideas:** My thought is to use the idea of black body radiation because black body radiation connects the two components that we need/want to know: temperature and wavelength.
 * Steps:**
 * Data/equation gathering:**

Then I found in the Message of Starlight article the **Wien's Law** that only required a few things: the peak wavelength in meters, Temperature in Kelvins, constant of proportionality, called Wien's displacement constant, that is equal to 2.897 7 685(51) × 10−3 m·K My new idea is to find a redshift adjusted wavelength of a star much line this: This is a redshift adjusted wavelength of the average of a hundred quasars.
 * Connections made:**

It looks like the Wien's Law graph:
 * Interesting fact I found out: that our sun is an average star in our galaxy because the star is in the middle of a common temperature range of the stars.

I did a example "problem" from the graph above (the 100 quasar wavelength). The peak wavelength is about 1100~01200nm. With a simple calculation (wien’s constant/wavelength). the temperature turns out to be about 2519.799K. From the color chart above this means that the color that we would see is like orange-light orange. Also that the quasar galaxies are made up of about middle to late aged stars. (White/blue= fairly infant stars, Red/orange=Old stars).
 * Solution and Example:**
 * I first found the peak wavelength:**
 * Then I applied Wien's Law**:
 * And Got:**
 * And inferred:**

My conclusion is that to find the average temperature of a star in a galaxy you need to find the redshift-adjusted spectra of the galaxy and the peak wavelength of the redshift-adjusted galaxy. Then use Wien's Law to find the average temperature of the galaxy. Some hazards/impediments are that a galaxy is not made up of just one kind of star. To compensate for the hazards we can find the most common star in the galaxy and then find the average temperature based on the common star's wavelength. To find the "common star" we can look a the **Hertzsprung - Russell Diagram** that shows us what kind of star it is based on its luminosity and temperature. As you can see we found the star to be around 2500K so according to the **Hertzsprung - Russell Diagram** it must be one (or more) of the following stars: Supergiants, Giants, and/or Main Sequence. We can more accurately know which star it is by finding the luminosity of the spectra explained here.
 * Conclusion:**
 * Cautions:**
 * Ways around the cautions:**
 * Hertzsprung - Russell Diagram:**