Color Index and Temperature

# Color Index and Temperature - lets you explore the...

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Color Index and Temperature Hot stars appear bluer than cooler stars. Cooler stars are redder than hotter stars. The ``B-V color index'' is a way of quantifying this using two different filters; one a blue (B) filter that only lets a narrow range of colors or wavelengths through centered on the blue colors, and a ``visual'' (V) filter that only lets the wavelengths close to the green-yellow band through. A hot star has a B-V color index close to 0 or negative, while a cool star has a B-V color index close to 2.0. Other stars are somewhere in between. Here are the steps to determine the B-V color index: 1. Measure the apparent brightness (flux) with two different filters (B, V). 2. The flux of energy passing through the filter tells you the magnitude (brightness) at the wavelength of the filter. 3. Compute the magnitude difference of the two filters, B - V. The UNL Astronomy Education program's Blackbody Curves and UBV Filters module

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Unformatted text preview: lets you explore the relationship between temperature and the thermal spectrum by manipulating various parameters with a graphical interface (link will appear in a new window). You can also explore temperature-color correlation using various filters. Wien's Law and Temperature Another way to measure a star's temperature is to use Wien's law described in the Electromagnetic Radiation chapter . Cool stars will have the peak of their continuous spectrum at long (redder) wavelengths. As the temperature of a star increases, the peak of its continuous spectrum shifts to shorter (bluer) wavelengths. The final way to measure a star's temperature is more accurate than the previous two methods. It uses the strength of different absorption lines in a star's spectrum. It is described in full a little later in the chapter. The temperatures of different types of stars are summarized in the Main Sequence Star Properties table ....
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## This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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Color Index and Temperature - lets you explore the...

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