A supermoon occurs when a full or new moon comes into its closest elliptical orbit to the Earth. The technical name for this phenomenon is perigee. A full moon at perigee is visually larger as seen in the Earth’s night sky—14% larger in diameter, 30% larger in area and shines 30% brighter.
In the Northern Hemisphere, supermoons will tend to appear larger during the winter.
The best time to enjoy a supermoon is after moonrise, weather permitting, when the moon is just above the horizon. A supermoon appears bigger and brighter than when it’s higher up in the sky because of the comparative size of the supermoon with the landscape – hills, foliage and buildings.
Civilizations throughout history have given this event various names—such as blood moon, harvest moon or hunter’s moon.
Sometimes a supermoon coincides with a lunar eclipse—which happened most recently September 27-28, 2015. It is not unusual for these eclipses to occur in a tetrad—4 lunar eclipses over the span of 2 years.