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Hertzsprung-Russell Diagram Uses
Overview H-R Diagrams can be used in a variety of stellar applications. A few of them are discussed below. Classification Because the horizontal axis is based upon stars' color, this can be extrapolated into a spectral classification. Stars that are in the same general region of the diagram share many similar properties. Therefore, based upon their position on the diagram, a star can be classified and its general properties are instantly known. For example, if I were to tell you that the sun was a type G star, you would know that it had a temperature of around 6000 K, a color of yellow, and an absolute magnitude of around +5. In actuality, the sun has a temperature of about 5,800 K, is yellow, and has a magnitude of +4.85*. You would also have an idea of what its spectrum looked like. *This is the sun's absolute magnitude, as opposed to its apparent magnitude. The Sun's apparent magnitude is -26.87. Apparent magnitude is a measure of how bright a star is from our vantage point here on Earth. The absolute magnitude is what the star's magnitude would be if it were viewed from a distance of 10 parsecs (approximately 33 light-years). Distance A second, very important, application of the H-R Diagram is the derivation of the distance to a star cluster or galaxy. In order to accomplish this, accurate H-R Diagrams are used, where the color and absolute magnitudes are known. With this, you know where the main sequence is supposed to be. Then, an H-R Diagram is made of the cluster or galaxy to which the distance is in question. Graphing the color and apparent magnitude, you get a similar H-R Diagram.
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