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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.
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.
Color temperature is a parameter describing ... the color temperature of an A0V star is about 15000 K ... to place a star on the HR diagram or to determine the ...
Modern observational versions of the chart replace spectral type by a color index (in diagrams made in the middle of the 20th Century, most often the B-V color) of the stars. This type of diagram is what is often called an observational Hertzsprung–Russell diagram, or specifically a color–magnitude diagram (CMD), and it is often used by ...
As this is the core temperature of a star with about 1.5 M ☉, the upper main sequence consists of stars above this mass. Thus, roughly speaking, stars of spectral class F or cooler belong to the lower main sequence, while A-type stars or hotter are upper main-sequence stars. [16]
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.
Star name Temperature ()Spectral type Distance (light years) Notes WISE 0855–0714: 285 Y4 7.426 ± 0.039 [9]WISE 0336-0143B [10]: 295 ± 10 [11]: Y1? 32.7 [12]: spectral type is not yet published, but should be around Y1 if we assume MIRI F480M is similar to W2 and by using Figure 13 from Kirkpatrick et al. 2012 [13] Might be a later spectral type.
In massive stars (greater than about 1.5 M ☉), the core temperature is above about 1.8×10 7 K, so hydrogen-to-helium fusion occurs primarily via the CNO cycle. In the CNO cycle, the energy generation rate scales as the temperature to the 15th power, whereas the rate scales as the temperature to the 4th power in the proton-proton chains. [2]