Why doesnt Jupiter produce light?

Jupiter doesn't produce light because it is not hot enough. It does, like the other planets and moons, reflect the Sun's light, and at this moment, (October 2011) it is the brightest object in the night sky after the Moon, and was easily seen even with the full moon in the sky.

It is a gas giant, and the density at the centre is possibly enough to initiate fusion, but hasn't. Perhaps its core is deficient in heavy material?

Jupiter and Saturn enjoy an harmonic dance with each other. Look up year lengths.