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The solar luminosity (L ☉) is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal solar luminosity is defined by the International Astronomical Union to be 3.828 × 10 26 W. [2]
In astronomy, this amount is equal to one solar luminosity, represented by the symbol L ⊙. A star with four times the radiative power of the Sun has a luminosity of 4 L ⊙. 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.
Under the present atmospheric composition, this past solar luminosity would have been insufficient to prevent water from uniformly freezing. There is nonetheless evidence that liquid water was already present in the Hadean [6] [7] and Archean [8] [6] eons, leading to what is known as the faint young Sun paradox. [9]
Solar irradiance varies systematically over the cycle, [69] both in total irradiance and in its relative components (UV vs visible and other frequencies). The solar luminosity is an estimated 0.07 percent brighter during the mid-cycle solar maximum than the terminal solar minimum.
For most objects in the solar system, the OC echo dominates and the most commonly reported radar albedo parameter is the (normalized) OC radar albedo (often shortened to radar albedo): [82] ^ = where the denominator is the effective cross-sectional area of the target object with mean radius, r {\displaystyle r} .
The luminosity thus obtained is known as the bolometric luminosity. Masses are often calculated from the dynamics of the virialized system or from gravitational lensing . Typical mass-to-light ratios for galaxies range from 2 to 10 ϒ ☉ while on the largest scales, the mass to light ratio of the observable universe is approximately 100 ϒ ...
Scientists said the sun is now in its solar maximum, or the peak of its 11-year solar cycle.
where M and L are the mass and luminosity of the star, respectively, is a solar mass, is the solar luminosity and is the star's estimated main-sequence lifetime. Although more massive stars have more fuel to burn and might intuitively be expected to last longer, they also radiate a proportionately greater amount with increased mass.