25 Jul 2014

Bright light in the night sky: Supermoons or perigean moons

Moon studies
(courtesy NASA, Clementine trackers)
By Marie Powell

We've all heard stories about the full moon making people and animals behave in strange ways. When the moon is full, we can see the whole "face" of the moon for three or four days. According to legend, the full moon can cause werewolves to change shape, and people to go mad or commit more crimes.

The full moon caught the public's attention this summer in another way. Each year, we experience times when the earth and moon come close together in their orbits. Astronomers, or scientists who study the solar system and celestial bodies like the moon (astronomy), call the point at which the moon's orbit is closest to the earth the "perigee," while the point farthest away is the "apogee." During some months, the earth and moon come closer together in orbit. These "perigean" moons may look brighter and larger than usual.

Astrologers, or those who see relationships between astronomy and people, call these moons "supermoons." This term is credited to astrologer Richard Nolle and has become popular in the media. 

The first of three perigean full-moons in 2014 occurred on July 12. According to some sources, the centre of the moon and the centre of the earth were about 361,800 km (224,800 mi) apart. We will see this "supermoon" again on August 10 and September 9. 

The full moon has a different name each month in folklore, and the name varies depending on whether you live in the northern or southern hemisphere. For example, the July full moon is known in the northern hemisphere as the Buck Moon (when deer grow antlers), Thunder Moon, or Hay Moon. Here are two interesting sites that show the various names of the full moon:

Almanac Full Moon Names:

For more information about the phases of the moon, check out these websites and articles:

Understanding Astronomy by Daniel V. Schroeder: 

Lunar phases of the moon (photographs) by Anthony Ayiomamitis:

Full moon calendars:

NASA (600 years of moon phases):
(This year is included here: http://eclipse.gsfc.nasa.gov/phase/phases2001.html)

For more information about the night sky, see Joan Marie Galat's "Observing the Night Sky" here on Sci/Why.

Marie Powell is the author of 15 books for children, including Dragonflies are Amazing (Scholastic Canada) and the Word Families series (Amicus Publishing).

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