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2. Solar luminosity - Wikipedia

   en.wikipedia.org/wiki/Solar_luminosity

   Evolution of the solar luminosity, radius and effective temperature compared to the present-day Sun. After Ribas (2010) [1] 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.

3. Sunrise equation - Wikipedia

   en.wikipedia.org/wiki/Sunrise_equation

   This plot was created using the simple sunrise equation, approximating the sun as a single point and does not take into account effects caused by the atmosphere or the diameter of the Sun. The sunrise equation or sunset equation can be used to derive the time of sunrise or sunset for any solar declination and latitude in terms of local solar ...

4. Luminosity - Wikipedia

   en.wikipedia.org/wiki/Luminosity

   For example, consider a 10 W transmitter at a distance of 1 million metres, radiating over a bandwidth of 1 MHz. By the time that power has reached the observer, the power is spread over the surface of a sphere with area 4πr 2 or about 1.26×10 13 m 2, so its flux density is 10 / 10 6 / (1.26×10 13) W m −2 Hz −1 = 8×10 7 Jy.

5. Color index - Wikipedia

   en.wikipedia.org/wiki/Color_index

   For comparison, the whitish Sun has a B−V index of 0.656 ± 0.005, [2] whereas the bluish Rigel has a B−V of −0.03 (its B magnitude is 0.09 and its V magnitude is 0.12, B−V = −0.03). [3] Traditionally, the color index uses Vega as a zero point.

6. Brightness temperature - Wikipedia

   en.wikipedia.org/wiki/Brightness_temperature

   For a black body, Planck's law gives: [8] [11] = where (the Intensity or Brightness) is the amount of energy emitted per unit surface area per unit time per unit solid angle and in the frequency range between and +; is the temperature of the black body; is the Planck constant; is frequency; is the speed of light; and is the Boltzmann constant.

7. Orders of magnitude (illuminance) - Wikipedia

   en.wikipedia.org/wiki/Orders_of_magnitude...

   Factor ()Multiple Value Item 0 0 lux 0 lux Absolute darkness 10 −4: 100 microlux 100 microlux: Starlight overcast moonless night sky [1]: 140 microlux: Venus at brightest [1]: 200 microlux

8. Magnitude (astronomy) - Wikipedia

   en.wikipedia.org/wiki/Magnitude_(astronomy)

   A more complex definition of absolute magnitude is used for planets and small Solar System bodies, based on its brightness at one astronomical unit from the observer and the Sun. The Sun has an apparent magnitude of −27 and Sirius, the brightest visible star in the night sky, −1.46. Venus at its brightest is -5.

9. Mass–luminosity relation - Wikipedia

   en.wikipedia.org/wiki/Mass–luminosity_relation

   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 ...