Jupiter and Moon

First Quarter Moon Near Jupiter

On January 30, 2012, the waxing moon will appear again near our giant planet Jupiter. Take a moment to look at this pairing high in the southwest sky after sunset. The moon will reach first quarter stage at 11:10 p.m. Central Time. At this stage the moon appears half-lit in sunshine and half-immersed in the moon’s own shadow. Our moon takes about 29.5 days to get through its phases as it orbits Earth. The moon is always half lit by the sun, but as it orbits Earth, we see different parts of this illumination that’s how we see the phases. When the moon is between the sun and Earth, then the backside of the moon is lit so we don’t see any lit part of the moon that is the new moon. As the moon orbits around the Earth, the moon is said to wax, getting larger in its phase towards first quarter. When the moon is at right angles with the sun and Earth, the moon appears half lit first quarter. When the Earth is between the sun and the moon, the moon appears fully lit the full moon. The moon continues in its orbit, waning, getting smaller towards last quarter. Then back to new moon taking a total of around 29.5 days.
source:www.earthsky.org