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The absolute magnitude M, of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of 10 parsecs (33 ly). The absolute magnitude of the Sun is 4.83 in the V band (visual), 4.68 in the Gaia satellite's G band (green) and 5.48 in the B band (blue).
For example, Betelgeuse has the K-band apparent magnitude of −4.05. [5] Some stars, like Betelgeuse and Antares, are variable stars, changing their magnitude over days, months or years. In the table, the range of variation is indicated with the symbol "var". Single magnitude values quoted for variable stars come from a variety of sources.
Betelgeuse is a red supergiant star in the constellation of Orion. It is usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in its constellation. It is a distinctly reddish, semiregular variable star whose apparent magnitude, varying between +0.0 and +1.6, has the widest range displayed by any first ...
Photographic magnitude (m ph or m p) is a measure of the relative brightness of a star or other astronomical object as imaged on a photographic film emulsion with a camera attached to a telescope. An object's apparent photographic magnitude depends on its intrinsic luminosity , its distance and any extinction of light by interstellar matter ...
Consequently, a magnitude 1 star is about 2.5 times brighter than a magnitude 2 star, about 2.5 2 times brighter than a magnitude 3 star, about 2.5 3 times brighter than a magnitude 4 star, and so on. This is the modern magnitude system, which measures the brightness, not the apparent size, of stars.
Accurate measurement of stellar luminosities is difficult, even when the apparent magnitude is measured accurately, for four reasons: The distance d to the star must be known, to convert apparent to absolute magnitude. Absolute magnitude is the apparent magnitude a star would have if it were 10 parsecs (~32 light
I.E. the adjustment to the standard relationship between absolute and apparent magnitude required to correct for the redshift effect. [4] Here, D L is the luminosity distance measured in parsecs . The exact nature of the calculation that needs to be applied in order to perform a K correction depends upon the type of filter used to make the ...
For objects within the immediate neighborhood of the Sun, the absolute magnitude M and apparent magnitude m from any distance d (in parsecs, with 1 pc = 3.2616 light-years) are related by = = (), where F is the radiant flux measured at distance d (in parsecs), F 10 the radiant flux measured at distance 10 pc.