Jupiter is the second brightest in the world after the sun
The Moon is illuminated by the Sun. At full moon, we see the bright part - the illuminated part. At new moon, we see mostly the dark part. (This part is also slightly visible, due to light reflected from the Earth.)
It is the sun
Even on Jupiter, or in the vicinity of Jupiter, the sun is still the brightest object in the sky. The brightest planet would be Saturn.
Jupiter is the second brightest planet in the sky after Venus and the fourth brightest object in the sky. The sun and the moon are the brightest objects in the sky, but they are not planets.
No. The Sun is
what is the second closest planet from the moon
Clouds would be second. Beyond earth's atmosphere the moon would be the brightest object in the sky, now followed by the International Space Station. Venus has been displaced from 3rd to 4th place. None of these objects shine with their own light, but from reflected light of our sun.
Um, Wouldn't that be the sun?!?!
Venus
The moon is the closest heavenly body to the earth and because of its relatively high albedo it reflects a lot of the light falling on it hence it is the brightest object in the night sky. Similar reasons also apply to Venus, which is also a very bright object.
There is only one star in the solar system, and that is Sol, our sun. All planets that form our solar system orbit around Sol -- there are no other stars in our solar system. The next closest star/solar system is Alpha Centuri, about 4.3 light years away.
Jupiter.