stellar+spec

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**__Stellar Spectroscopy-Summary__**
__**Intro and definitions**:__


 * Spectroscopy** is the study of light we see from an object.

We measure the amount and color/wavelengths of the light involved. It is possible to measure all of the spectrums from gamma rays to radio waves in other words: if a light or energy is produced, absorbed or reflected by an object we can know what it is through spectroscopy (but the colder the object – the harder it gets to figure it out).


 * Three Types of Spectra: Continuous, Emission line, absorption line.**

EX: the sun is hot and dense, it produces the light to us which is the visible spectrum.
 * Continuous** is all wavelengths of light produced by hot, dense objects.

EX: hydrogen gas, when electricity runs through it, gives off a couple of spectra. I think this could also be like neon lights that are filled with argon and other noble gases (most likely).
 * Emission** line is a short wavelength produced by hot, low-density objects.

EX: any gas
 * Absorption** line is a wavelength absorbed by cool gas/gases (the light comes from a different source). It absorbs what ever wavelength it would usually emit at high temperatures.

These spectra lines (emission and absorptions) are caused by ionized atoms. The atoms become ionized when electrons are stripped away from the atom. Hotter = more ionized.

A star has a hot interior and a cooler “atmosphere”.
 * Continuous Spectrum**

The dense interior creates a **blackbody continuum** (a continuous spectrum) but it isn’t dependent on the composition of the star just the temperature. So in a sense it is how hot the star is: hot stars (>10,000K) is a blue-ish color, cool stars (<4,000K) a red-ish color, and in between (~6,000K) is a yellow-white color.

We can find the relationship between temperature and color (wavelength) through the **Wien’s Law**.