QUESTION:  Since Neptune is now the farthest planet from the sun, just how
much light is there, and what kind of light on Earth could you compare it with?

ANSWER from Heidi Hammel on May 29, 1996:

There would not be much light on Neptune.  From Neptune, the Sun would look
like no more than a very bright star.  The Sun would also be so distant that
in addition to being very faint, it also wouldn't give much warmth.  The
cloud-tops on Neptune are always very cold,  about -220 F!

What kind of light would I compare it with on Earth?  Well, it is still
sunlight, so the color would be the color of sunlight (in other words, all
colors combining to be "white").  But there would be very little sunlight.
Imagine being outside on the darkest night you can think of.  Make sure that
in your imaginary dark night that there is no Moon; that is much too bright.
Now, in your very very dark night, imagine that there is one star that is
definitely a bit brighter than the other stars, not as bright as our Moon,
but still pretty obvious. That would be the Sun.