AlexT wrote:
Folks

Reading through various articles about the upcoming launch of the New
Horizon probe I did not manage to locate any solid information about
the amount of energy & light available from the Sun on Pluto.

I remember having read something like "about the size and brightness
of Venus as seen from earth".

If it's true I find it really remarkable that an earth based
telescope would manage to "see" Pluto...


--alexT


The brightness of an object at a given distance requires knowledge of
the luminosity of the light-emitting object and that distance via:

b = L/(4pi)d^2

The luminosity of the Sun is 3.9 x 10^26 Watts and the average distance
to Pluto is 5.916 x 10^12 meters. This will tell you the watts/square
meter at Pluto. To compare it to what we get here, put in the Earth's
average distance of 1.5 x 10^11 meters or do ratios of the equation for
Pluto compared to here, eliminating the L/(4pi) term.

The ratio of brightness number can be used to determine the magnitude of
the Sun compared to its magnitude he

m(E)-m(P) = 2.5 log [(b(P)/b(E)]

m(E) = -26.8, so you can do the ratio of brightness of Pluto to Earth to
calculate the magnitude of the Sun at Pluto. Venus at its most
brilliant comes in about -4.4, so you can check your answer against that
marker to answer your question.