Photographs or other instruments can tell the difference between a supermoon and ordinary full moon. The supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). Image by Marco Langbroek of the Netherlands via Wikimedia Commons.
Moon is Earth’s only natural satellite and the second brightest object in the sky after the sun.
The moon’s gravity can cause small ebbs and flows in the continents called land tides or solid Earth tides. These are greatest during the full and new moons because the sun and moon are aligned on the same or opposite sides of the Earth.
So, the moon is full, or opposite Earth from the sun, once each month. It’s new, or more or less between the Earth and sun, once each month.
Every month, as the moon orbits Earth, it comes closest to Earth - that point is called perigee.
The moon always swings farthest away once each month - that point is called apogee.
The astrologer Richard Nolle coined the term supermoon over 30 years ago. The term has only recently come into popular usage.
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| Image and caption via NOAA. * a) |
A full moon is the opposite of a new moon. At both the new and full phases, the moon is on a line with the Earth and sun. At new moon, the moon is in the middle position along the line. At full moon, Earth is in the middle. Full moon always comes about two weeks after new moon, when the moon is midway around in its orbit of Earth, as measured from one new moon to the next.
* a) About three or four times a year, the new or full moon coincides closely in time with the perigee of the moon—the point when the moon is closest to the Earth. These occurrences are often called ‘perigean spring tides.’ The difference between ‘perigean spring tide’ and normal tidal ranges for all areas of the coast is small. In most cases, the difference is only a couple of inches above normal spring tides.
* a) About three or four times a year, the new or full moon coincides closely in time with the perigee of the moon—the point when the moon is closest to the Earth. These occurrences are often called ‘perigean spring tides.’ The difference between ‘perigean spring tide’ and normal tidal ranges for all areas of the coast is small. In most cases, the difference is only a couple of inches above normal spring tides.
So, the moon is full, or opposite Earth from the sun, once each month. It’s new, or more or less between the Earth and sun, once each month. Every month, as the moon orbits Earth, it comes closest to Earth - that point is called perigee.
The moon always swings farthest away once each month - that point is called apogee.
The astrologer Richard Nolle coined the term supermoon over 30 years ago. The term has only recently come into popular usage.
Richard Nolle has defined a supermoon as:
… a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit.
That’s a pretty generous definition and allows for many supermoons. By this definition, according to Nolle there are 4-6 supermoons a year on average.
In the year 2011 the media used the label "supermoon" to describe the full moon of March 19, 2011.and this label became familiar.
… a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit.
That’s a pretty generous definition and allows for many supermoons. By this definition, according to Nolle there are 4-6 supermoons a year on average.
In the year 2011 the media used the label "supermoon" to describe the full moon of March 19, 2011.and this label became familiar.
On that date, the full moon aligned with proxigee – the closest perigee of the year – to stage the closest, largest full moon of 2011.
Conclusion:
Supermoons are full moons that coincide with "lunar perigee," when the moon's orbit brings it closest to Earth. This moon appears bigger and brighter than a typical full moon.
Source: Wikipedia, http://earthsky.org, internet
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