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In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or hotter) the object is. Conversely, the larger the color index, the more red (or cooler) the object is.
The apparent magnitudes of stars in the system are often used to determine the color indices B−V and U−B, the difference between the B and V magnitudes and the U and B magnitudes respectively. [1] The system is defined using a set of color optical filters in combination with an RMA 1P21 photomultiplier tube. [2]
Effective temperature of a black body compared with the B−V and U−B color index of main sequence and supergiant stars in what is called a color-color diagram. [1] Stars emit less ultraviolet radiation than a black body with the same B−V index. Although stars are not perfect blackbodies, to first order the spectra of light emitted by stars ...
Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, whereas more-evolved stars – in particular, newly-formed white dwarfs – can have surface temperatures above 100,000 K. [3] Physically, the classes indicate the temperature of the star's atmosphere and are normally listed from hottest to coldest.
This was done so the color index of these stars would be 0. [13] Although this system is often called "Vega normalized", Vega is slightly dimmer than the six-star average used to define magnitude 0.0, meaning Vega's magnitude is normalized to 0.03 by definition.
Thursday's incoming geomagnetic storm has a Kp index 8, meaning the auroras will move even further towards the equator and become very bright and very active, according to NOAA.
Where will the northern lights be visible tonight? The northern lights will be visible for parts of the northern U.S., according to the NOAA Space Weather Prediction Center's aurora forecast.The ...
The Detroit Red Wings visit the Dallas Stars tonight at 8 p.m. Monday, Dec. 11, 2023, at American Airlines Center in Dallas.