Waxing Gibbous

The Moon is Earth’s only natural satellite, with a mean diameter of 3,474 km and an average distance of about 384,400 km. It formed roughly 4.5 billion years ago, probably after a giant impact early in Solar System history. Its rotation is synchronous with its orbit: it turns once in about 27.3 days, keeping the same hemisphere generally facing Earth, while its cycle of phases takes 29.53 days.

At 75% illumination the Moon is in a waxing gibbous phase, between first quarter and full Moon. The terminator — the line dividing the lit and unlit halves — lies closer to the lunar limb, so much of the near side is sunlit while low-angle sunlight still emphasizes relief near the shadow boundary. The bright lunar highlands are ancient, heavily cratered anorthositic crust, while the darker maria are basaltic plains formed by volcanic flooding billions of years ago. The Moon’s apparent diameter is about 0.5 degrees, varying slightly with its distance from Earth.