In other words, it won’t just be a supermoon, it will be the closest supermoon of the year, and such proximity to our planet will not be repeated again until August 2014.
Astronomers call this a perigee full moon. The word perigee describes the moon’s closest point to Earth for a given month.
Two years ago, when the closest and largest full moon fell on March 19, 2011, many used the term supermoon, which we’d never heard before. Last year, we heard this term again to describe the year’s closest full moon on May 6, 2012.
Now the term supermoon is being used with greater frequency. Last month’s full moon – on May 24-25 – was also a supermoon. But the June full moon will be even more super! The closer the timing of a full moon to the time of perigee, the closer the moon will be to Earth. This month, the crest of the moon’s full phase and the perigee fall within an hour of each other.
For many, the moon will appear about as full on the evening of June 22nd as on the evening of the 23rd.
What does “supermoon” mean exactly?
Until a few years ago, the term was not often used in astronomy. To the best of our knowledge, the term supermoon was coined by the astrologer Richard Nolle over 30 years ago, but is only now coming into popular usage.
Nolle has defined a supermoon as “a new or full moon which occurs with the moon at or near (within 90 percent of) its closest approach to Earth in a given orbit”.