Temperature total brightness

The temperature derived from this equation is called the total brightness temperature and is measured by determining the total illumination (E) emitted by the hot source. If reabsorption by cool gases does occur then corrections must be made. 

We shall now provide a second example to illustrate step-by-step calculations. In this example a flare stack is estimated to be 80% efficient in combusting HjS off-gas. The total off-gas through the stack is 400,000 kg/hr, of which 7.0 weight percent is H2S. The physieal stack height is 250 m, the stack diameter is 5.5 m, and the stack emission velocity is 18 m/s. The stack emission temperature is 15°C. The meteorological conditions may be described as a bright sunny day with a mean wind speed of 3 m/s. 

Commercial elemental sulfur is usually of bright-yellow color at 20 °C [36]. Pure orthorhombic a-Ss is, however, of greenish-yellow color at 20 °C but totally colorless at 77 K while commercial sulfur often remains pale-yellow at this temperature [59]. The reasons for this different behavior are twofold. Commercial samples are never pure Ss but besides traces of organic impurities they always contain Sy in concentrations of between 0.1 and 0.5% [59]. Sulfur found as a mineral in Nature sometimes also contains Sy but in addition traces of selenium are quite often present (up to 680 ppm Se, probably as SySe molecules) [60]. These minor components influence the color of the samples at ambient and low temperatures in the sense that a more orange-type of yellow ( egg-yellow ) is recognized. 

In 1879, Josef Stefan investigated the increasing brightness of a black body as it is heated and discovered that the total intensity emitted over all wavelengths increases as the fourth power of the temperature (Fig. 1.5). This quantitative result is now called the Stefan-Boltzmann law and is usually written... 

Thus, by measuring the gas temperature T, and the slope of the gas density distribution (or that of the surface brightness distribution), the radial distribution of the total gravitating mass can be found. 

Pyrometric thermometers can be of the following types optical (brightness), ratio (two-color), total (wide-band), and narrow-band, whereas the fiber optic designs can be of the light-pipe, black body, dual-wavelength, crystal, gap, and fluoroptic variety. Their temperature ranges are from -40 to 4,000°C (-40 to 7,000°F), and their errors range from 0.25% to 2% FS. 

There are also brown dwarfs to consider. Brown dwarfs are astronomical objects somewhat between a planet and a star and have a mass less than 0.08 times the mass of our sun and a surface temperature below 2,500 K. (As comparison, the cool red dwarfs are about 3,000-3,400 K). A large number of brown dwarfs would not change how bright the Galaxy appears in optical observations but would change its total mass quite substantially. 

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