The last supermoon of the year will soon shine in December skies. When a full moon is closer to Earth in its orbit, a so-called supermoon happens. It makes the moon look up to 14% bigger and 30% brighter than the faintest moon of the year. Thursday night’s supermoon is the last of three in a row this year. It can be glimpsed in clear night skies without any special equipment. But it can be tough to discern the subtle change with the naked eye. Supermoons happen a few times a year.