OK, I have to ask. How many photons do you think the Sun produces in a year?

Question

oops. how many photons are emitted, not just produced.

Answer 1

This can be calculated, but a clarification is necessary. Do you mean how many photons escape the sun each year, or how many are created and scattered and absorbed and re-emitted throughout the Sun?
"oops. how many photons are emitted, not just produced."

[EDIT]
OK, now you are cooking with gas! A decent approximation would be to assume all of the energy is emitted at the peak of the Planck spectrum for a 5780 degree K object the size of the sun and divide that by the energy of a photon at that particular frequency and then multiply by the number of seconds in a year (about Pi*3*10^7, conveniently).

A more precise approximation is to actually integrate from 0 to Infinity hertz the Planck Spectrum over the energy of a single photon and multiply by area of the solar photosphere again seconds in a year. (Without "the energy of a photon" divisor in the integrand, you will derive the Stefan-Boltzmann law with this integral).

You still mess up a bit since some is absorbed and re-emitted by the chromosphere and some more is actually generated in the corona, however I am confident these corrections (especially the latter) will be orders of magnitude smaller, so the result should be good to a few significant figures, assuming the photosphere radius and temperature numbers are precise enough.

OK, now I am gonna make these calculations and then I will edit again with the answers. (How much credit do I get for saying how to solve the problem w/o actually doing it?)

[EDIT]
With the first method, I divide 3.85*10^26 J/s by the energy of a 501.4nm photon and multiply the seconds in a year to get 3*10^53 photons. Bright.

With the second method, I am getting a number several orders of magnitude off from here which probably means I have done the integral over frequency incorrectly. I will take some time going back over it later. I am tired of it now. In the first method, I just used the Stefan Boltzmann constant to calculate the total luminosity and then divided by the individual photon energy so this is simpler and I trust it, over deriving my own "photon count" Stefan-Boltzmann law.

[Final Edit]
I had an extra factor of the speed of light in there. Got careless with the exponent on c going from line to line in my calculation. for the second method, I ended up with 5.63*10^52 photons/year, with dubious certainty on the last siginificant figure there, but I'll wager the first two are good.

If you want to check my work, the best way is to examine my photon-count Stefan-Boltzmann eqn:

I came up with 4*pi*R^2*T^3*1.5205*10^15 = photons/sec for a sphere. This next bit may be of interest to astronomy types with a little calculus experience. That T^3 (instead of the traditional T^4 for the energy Stefan-Boltzmann eqn) happens because you lose a power of frequency in the numerator of the integrand. When you do the u substitution to simply the exponential function in the denominator you end up with on less power of "T" in the constant outside of the integral.

I neglected the oblateness of the sun in addition to assuming a smooth planck spectrum with no emission or absorption lines superposed on top. Thanks for the fun question!

Answer 2

Unfortunately that particular question is beyond a scientific answer.

We don't know anywhere near enough about the sun's interior processes to answer that or even provide a ballpark estimate that has any hope of being close.

We can compute with a fair ballpark figure how much of its energy radiates into space in one year though, but since that's not the question, I won't bother to make that computation. It's possible, but too time consuming at the moment.

Cheers.
 

Answer 3

Everytime the sun fuses 2 hydrogen atoms into a helium atom, it emits a photon.

Answer 4

on the planet of quorple the quorplings had built a computer that count caculate the most infiite of numbers.it had determined how many grains of sand are in all the beaches in
satraginus 5.It had calculated how many altarian dollras all the precious metals on all the planets in the scorpio system.It even figured the number of all the molecules present in Magrathea.when programmed to calculate how many photos a star produces in a year,the computer quickly overheated.

Answer 5

Why do you need to know?
How about you spend some time counting all the grains of sand on the beaches from Baja, California to Vancouver, Wash. Makes about as much sense

Answer 6

42 to the power of 42 x 42 to the power of 42.

I am the Fringe and I love outer space.

Answer 7

is this anything like "guess how many beans are in this jar and win a prize"?

Answer 8

42.

Answer 9

10^40photons I guess.

Answer 10

Thanks for asking Bill, cuz I know the answer!
Drum roll... a lot!

;-D No need to thank me.