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| radiation measurement |
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Kinds of radiation measurement :
- color
- luminosity (1 kind, 8 facts) - Brightness of a celestial body, measured in terms of (apparent) magnitude, absolute magnitude, or using the Sun's brightness as 1.0 on a solar scale. The luminosity of a star corresponds with its internal radiation pressure, which in turn depends on its mass., The total amount of energy radiated by a star - that is, its true, or intrinsic, brightness., The intrinsic brightness of a star. Usually defined in terms of absolute magnitude., Total radiant energy output per second (absolute brightness, usually expressed in ergs s-1 or in magnitudes). L = 4πR2σT4 (see Stefan's law).
- magnitude (14 kinds, 47 facts) - A logarithmic brightness scale for astronomical objects. See Appendix., The measured brightness of a celestial body. dim objects have magnitudes of high numbers, bright objects have magnitudes of low or even negative numbers. Seen from earth, stars of (apparent) magnitude 6 or higher cannot be detected with the naked eye. The Full Moon has a magnitude of -11, and the Sun one of -26.8. in order to standardize measurements of the brightness of more distant objects, the system of absolute magnitude is used. A measure of the radiation at all wavelengths emitted by a star is known as the bolometric magnitude., The measure of a star's brightness. apparent magnitude measures a star's apparent brightness - that is, how bright a star looks from Earth. absolute magnitude measures a star's intrinsic brightness - that is, how much light the star actually emits., The brightness of a star or planet, expressed on a scale in which lower numbers mean greater brightness. Apparent magnitude indicates the brightness of objects as we see them from earth, regardless of their distance. Absolute magnitude is defined as the apparent magnitude a star would have if viewed from a distance of ten parsecs, or 32.6 light-years. each step in magnitude equals a difference of 2.5 times in brightness: the brightest stars in the sky are apparent magnitude 1; the dimmest, 6. The magnitudes of extremely bright objects are expressed in negative values - e.g., the apparent magnitude of the Sun is about -26., An arbitrary number, measured on a logarithmic scale, used to indicate the brightness of an object. Two stars differing by 5 mag differ in luminosity by 100. 1 magnitude is the fifth root of 100, or about 2.512. The brighter the star, the lower the numerical value of the magnitude (see also Pogson's ratio)., A measure. on a logarithmic scale, used to indicate the brightness of a celestial object. A 1-magnitude difference in brightness between two stars corresponds to a difference in luminosity by 100.4 or 2.51; 5 magnitudes corresponds to factor of 100 in luminosity.
- spectral feature (87 kinds, 284 facts) - A feature in the spectra of a celestial object which occurs at a specific wavelength or range of wavelengths
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