How many photons does our sun emit in a second? I would assume that given that the earth receives about 1350 W/m^2 from the sun there is some calculation involving the size of the sun (radius 696,000 kilometers) and its distance from earth (146 million km) and photons per watt at the color temperature of the sun (5500K or so) that could be used to derive this. But I have no idea how to go about it. Or if perhaps there is a better way to find this out. I've found another question on here stating that the Sun's luminosity is 3.839 * 10^26. But I don't know how to convert that to photons either.


closed as off-topic by John Rennie, Kyle Kanos, Jon Custer, Daniel Griscom, peterh Dec 1 '17 at 5:32

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – John Rennie, Kyle Kanos, Jon Custer, Daniel Griscom, peterh
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Don't worry too much about photons in contexts like these. See, e.g., this answer and Lamb Jr.'s Anti photon (e-print). $\endgroup$ – stafusa Nov 29 '17 at 20:46

Here is the spectrum of the sun versus power.


Take a specific frequency, divide the yellow power value with h*nu, h the planck constant nu the frequency , and you will find the number of photons at that frequency per meter square arriving on the earth before the atmosphere ( it will be a huge number because h is small). If you integrate over the yellow spectrum you will have the number of photons within the limits of the spectrum. The answer can be extrapolated to the sun, but it will give the number of photons within the limits of this spectrum.

At the location of the sun the infrared and below frequencies should also be added to the spectrum , and that can only be done with a specific model of the sun and its energy creation. This is a first estimated because the "atmosphere" of the sun which is plasma also radiates gamma rays which are missing in the spectrum arriving at earth.

With the planck constant of 6.626070040(81)×10^−34 the only real answer to how many photons is "very large".


Not the answer you're looking for? Browse other questions tagged or ask your own question.