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Nonthermal sources can have very high brightness temperatures. In pulsars the brightness temperature can reach 10 30 K. [9] For the radiation of a helium–neon laser with a power of 1 mW, a frequency spread Δf = 1 GHz, an output aperture of 1 mm 2, and a beam dispersion half-angle of 0.56 mrad, the brightness temperature would be 1.5 × 10 10 ...
A branch of physics that studies atoms as isolated systems of electrons and an atomic nucleus. Compare nuclear physics. atomic structure atomic weight (A) The sum total of protons (or electrons) and neutrons within an atom. audio frequency A periodic vibration whose frequency is in the band audible to the average human, the human hearing range.
A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.
Brightness is the polar opposite of darkness. ... Scientific. Luminosity; Brightness (sound) Brightness temperature; Surface Brightness; Artistic. The Brightness, ...
As defined by the US Federal Glossary of Telecommunication Terms , "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light. [3] Brightness is an antonym of "dimness" or "dullness". With regard to stars, brightness is quantified as apparent magnitude and absolute magnitude.
For example, consider a 1 Jy signal from a radio source at a redshift of 1, at a frequency of 1.4 GHz. Ned Wright's cosmology calculator calculates a luminosity distance for a redshift of 1 to be 6701 Mpc = 2×10 26 m giving a radio luminosity of 10 −26 × 4 π (2×10 26) 2 / (1 + 1) (1 + 2) = 6×10 26 W Hz −1.
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[1] [2] [3] A more fundamental statement was later labelled as the zeroth law after the first three laws had been established. The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium ...