Astronomy Section 2.3 and 2.4 Notes Oct32010 2.3 The Moon, Out Constant Companion 13 Takes moon 27 days to orbit Earth. Takes 27 days for each circuit through constellations. Lunar phases: The state determined by the portion of the visible face of the Moon that is illuminated by sunlight. During full moon, we see half the moon that is lit by sunlight. During new moon we dont see the moon because the sun isnt illuminating the part we see at all. 12 Each cycle of phases from one new moon to the next takes apprx. 29 days. Longer than Earths orbital period bc o Earths motion around sun during time moon is orbiting Earth.