An extra-super supermoon is rising this evening, and you don't want to miss it.
Tonight's full moon will appear bigger and brighter in the night sky than it has in nearly 70 years, and all you have to do to witness its shining glory is look up.
"Supermoon" is a non-technical term for a moon that turns full at the same time it hits perigee — the point on its orbit when it is closest to Earth. The moon's path around our planet is shaped more like an oval than a circle, so there are times when it is closer to us (perigee) and times when it is farther away (apogee).
Supermoons occur about once every 14 months on average. However, Sunday night's supermoon is extra super because the moon will be even closer to Earth than usual.
At its closest approach, the moon will be 221,524 miles from our planet, compared with an average distance of 238,900 miles.
The last time the moon sailed this close to Earth was on Jan. 26, 1948, when it came 30 miles closer. The next time won't be until Nov. 24, 2034, when the distance between the two bodies will be 40 miles less.
Why does the distance between the Earth and the moon fluctuate so much?
As Bob King explained in Sky & Telescope, the shape of the moon's orbit varies due to the ever-changing distances and relative position of the sun, moon and Earth. Thanks to variations in these gravitational forces, the moon's orbit is sometimes more oval shaped, and other times more like a circle.
"When more oval, the Moon's perigee point gets unusually close to Earth, and if a full Moon arrives at that point, it will be considerably closer to us than during those times when the lunar orbit more closely resembles a circle," King wrote.
Astronomers warn that some skywatchers may be disappointed by this particular lunar show. At its closest (3:23 a.m. Monday morning) the lunar disk will appear 7% larger across, and 16% brighter than an average moon. Many people will not notice a difference, they warn.
But I say — don't underestimate the power of suggestion. If you take a minute to gaze upon our glowing, gorgeous moon, and remember that it is closer to us right now than it has been in more than half a century, I bet you anything it will look a little more special and super than usual.
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