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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 ...
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 ...
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 ...
The latter is commonly measured in W⋅nm −1. Φ e,λ [nb 7] watt per metre W/m M⋅L⋅T −3: Radiant intensity: I e,Ω [nb 8] watt per steradian: W/sr: M⋅L 2 ⋅T −3: Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity. Spectral intensity: I e,Ω,ν [nb 6] watt per steradian ...
The first list shows a few of the known stars with an estimated luminosity of 1 million L ☉ or greater, including the stars in open cluster, OB association and H II region. The majority of stars thought to be more than 1 million L ☉ are shown, but the list is incomplete. The second list gives some notable stars for the purpose of comparison.
It has a magnetic field with a strength in the range 10.5–130.5 Gauss [11] and it is an X-ray source with a luminosity of about 10 30 erg s −1. [5] The system displays an excess emission of infrared radiation , which would suggest the presence of a circumstellar disk of dust, [ 12 ] but these claims were later found to be doubtful.
This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period (which can be measured in seconds). In comparison, if the Sun's current luminosity is the same as its average luminosity over its lifetime, it would release 3.827 × 10 26 W × 3.1536 × 10 7 s/yr × 10 10 yr ≈ 1.2