Skywatchers around the world had a chance to observe the so-called "supermoon" in all of its glory on Monday Nov. 14. A supermoon happens when a full moon or new moon coincides with the moon's closest approach to Earth; also called perigee. The recent supermoon was especially “super” because it was the closest full moon to Earth since 1948. We won’t see another supermoon like this until 2034.
The moon’s orbit around Earth is slightly elliptical so sometimes it is closer and sometimes it’s farther away. When the moon is full as it makes its closest pass to Earth it is known as a supermoon. At perigee — the point at which the moon is closest to Earth — the moon can be as much as 14 percent closer to Earth than at apogee, when the moon is farthest from our planet. The full moon appears that much larger in diameter and because it is larger shines 30 percent more moonlight onto the Earth.
Supermoon is not an official astronomical term. It was first coined by an astrologer, Richard Nolle, in 1979. He defined it as ‘a new or a full moon that occurs when the moon is at or near (within 90 percent of) its closest approach to Earth in its orbit’. It is not clear why he chose the 90 percent cut off in his definition.
The technical term for a supermoon is perigee-syzygy of the Earth-moon-sun system. In astronomy, the term syzygy refers to the straight-line configuration of three celestial bodies. When the moon is close to the lunar nodes of its path during syzygy, it causes a total solar eclipse or a total lunar eclipse.
|‘Supermoon rises above The Narrows, on the Swan River, Perth, Western Australia.’ Photograph: Gorewell/GuardianWitness|
The biggest and brightest moon for observers in the United States was on Monday morning just before dawn. On Monday, Nov. 14, the moon was at perigee at 6:22 a.m. EST and “opposite” the sun for the full moon at 8:52 a.m. EST (after moonset for most of the US). It was the second of three supermoons set to occur by the end of 2016.
The best time to enjoy a super full moon is after moonrise when the moon is just above the horizon, weather permitting. At this position, a super full moon will look bigger and brighter than when it's higher up in the sky because you can compare the apparent size of the moon with elements in the landscape like hills, foliage, and buildings. This effect is called the "moon illusion".