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One nominal solar luminosity is defined by the International Astronomical Union to be 3.828 × 10 26 W. [2] The Sun is a weakly variable star, and its actual luminosity therefore fluctuates. [3] The major fluctuation is the eleven-year solar cycle (sunspot cycle) that causes a quasi-periodic variation of about ±0.1%. Other variations over the ...
L S, L ☉ - luminosity of the Sun; Luminosity of certain object: ... M [1] - mass of black hole; M acc - mass of accretion disc; Metallicity comparison
More recent modeling studies have shown that the Sun is currently 1.4 times as bright today than it was 4.6 billion years ago (Ga), and that the brightening has accelerated considerably. [8] At the surface of the Sun, more fusion power means a higher solar luminosity (via slight increases in temperature and radius), which is termed radiative ...
Luminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. [1] [2] In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects. [3] [4]
The relationship is represented by the equation: = where L ⊙ and M ⊙ are the luminosity and mass of the Sun and 1 < a < 6. [2] The value a = 3.5 is commonly used for main-sequence stars. [ 3 ] This equation and the usual value of a = 3.5 only applies to main-sequence stars with masses 2 M ⊙ < M < 55 M ⊙ and does not apply to red giants ...
Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of 10 parsecs (33 light-years; 3.1 × 10 14 kilometres; 1.9 × 10 14 miles). Therefore, it is of greater use in stellar astrophysics since it refers to a property of a star regardless of how close it is to Earth.
This two-dimensional (temperature and luminosity) classification scheme is based on spectral lines sensitive to stellar temperature and surface gravity, which is related to luminosity (whilst the Harvard classification is based on just surface temperature).
It groups stars into five main luminosity groups designated by roman numerals: I supergiant; II bright giant; III giant; IV subgiant; V dwarf (main sequence). Specific to supergiants, the luminosity class is further divided into normal supergiants of class Ib and brightest supergiants of class Ia. The intermediate class Iab is also used.