Solar luminosity Information & Solar luminosity Links at HealthHaven.com

The solar luminosity, L_☉, is a unit of luminosity or radiant power (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars. It is equal to the current accepted luminosity of the Sun, which is 3.839 × 10²⁶ W, or 3.839 × 10³³ erg/s.^[1] The value is slightly higher, 3.939 × 10²⁶ W (equivalent to 4.382 × 10⁹ kg/s or 2.107 × 10⁻¹⁵ M_☉/d) if the solar neutrino radiation is included as well as electromagnetic radiation.^[2] The Sun is a weakly variable star and its luminosity therefore fluctuates. The major fluctuation is the eleven-year solar cycle (sunspot cycle), which causes a periodic variation of about ±0.1%. Any other variation over the last 200–300 years is thought to be much smaller than this.^[2]

[edit] Determination

The solar luminosity is related to the solar irradiance measured at the Earth or by satellites in Earth orbit. The mean irradiance at the top of the Earth's atmosphere is sometimes known as the solar constant, I_☉. Irradiance is defined as power per unit area, so the solar luminosity (total power emitted by the Sun) is the irradiance received at the Earth (solar constant) multiplied by the area of the sphere whose radius is the mean distance between the Earth and the Sun:

$L_\odot = 4\pi kI_\odot A^2\,$

where A is the unit distance (the value of the astronomical unit in metres) and k is a constant (whose value is very close to one) that reflects the fact that the mean distance from the Earth to the Sun is not exactly one astronomical unit.

[edit] References

^ Carroll, Bradley W.; Ostlie, Dale A. (2007), An Introduction to Modern Astrophysics, Pearson Addison-Wesley, pp. Appendix A, ISBN 0-8053-0402-9
^ ^a ^b Noedlinger, Peter D., "Solar Mass Loss, the Astronomical Unit, and the Scale of the Solar System", Celest. Mech. Dynam. Astron., http://arxiv.org/ftp/arxiv/papers/0801/0801.3807.pdf

[edit] Further reading

Sackmann, I.-J.; Boothroyd, A. I. (2003), "Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars", Astrophys. J. 583 (2): 1024–39, doi:10.1086/345408, http://adsabs.harvard.edu/abs/2003ApJ...583.1024S
Foukal, P.; Fröhlich, C.; Spruit, H.; Wigley, T. M. L. (2006), "Variations in solar luminosity and their effect on the Earth's climate", Nature 443: 161–66, doi:10.1038/nature05072, http://www.nature.com/nature/journal/v443/n7108/abs/nature05072.html
Pelletier, Jon D. (1996), "Variations in Solar Luminosity from Timescales of Minutes to Months", Astrophys. J. 463: L41–L45, doi:10.1086/310049, http://www.iop.org/EJ/article/1538-4357/463/1/L41/5605.text.html
Stoykova, D. A.; Shopov, Y. Y.; Ford, D.; Georgiev, L. N.; Tsankov, L. (1999), "Powerful Millennial-Scale Solar Luminosity Cycles and Their Influence Over Past Climates and Geomagnetic Field", Proceedings of the AGU Chapman Conference: Mechanisms of Millennial Scale Global Climate Change, http://www.ncdc.noaa.gov/paleo/chapconf/stoykova_abs.html

[edit] External links

[0] Carroll, Bradley W.; Ostlie, Dale A. (2007), An Introduction to Modern Astrophysics, Pearson Addison-Wesley, pp. Appendix A, ISBN 0-8053-0402-9

[Noed-1] Noedlinger, Peter D., "Solar Mass Loss, the Astronomical Unit, and the Scale of the Solar System", Celest. Mech. Dynam. Astron., http://arxiv.org/ftp/arxiv/papers/0801/0801.3807.pdf

[1]

[2]

Contents

[edit] Determination

[edit] References

[edit] Further reading

[edit] External links