Stargazers wonder at annual 'Supermoon' Stargazers throughout large parts of the world stared up on Saturday night to witness the once-a-year Supermoon. The phenomenon occurs when the Moon is in perigee - its closest point to the Earth. The satellite follows an elliptical path around the planet, with one side about 31,000 miles (50,000 km) closer than the other, known as apogee. The Moon will seem especially big and bright since it will reach its closest spot to Earth at the same time it is in its full phase, according to Nasa. In the US, hundreds of amateur and professional astronomers turned out at the Griffith Park Observatory in Los Angeles to get a clear view of the rare occurrence.