Supermoon

A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its orbit—resulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth. The technical name is a perigee syzygy (of the Earth–Moon–Sun system) or a full (or new) Moon around perigee. Because the term supermoon is astrological in origin, it has no precise astronomical definition. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found. The opposite phenomenon, an apogee syzygy or a full (or new) Moon around apogee, has been called a micromoon.

A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its orbit—resulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth. The technical name is a perigee syzygy (of the Earth–Moon–Sun system) or a full (or new) Moon around perigee. Because the term supermoon is astrological in origin, it has no precise astronomical definition. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found. The opposite phenomenon, an apogee syzygy or a full (or new) Moon around apogee, has been called a micromoon.

Definitions

The name supermoon was coined by astrologer Richard Nolle in 1979, in Dell Horoscope magazine arbitrarily defined as: He came up with the name while reading Strategic Role Of Perigean Spring Tides in Nautical History and Coastal Flooding, published in 1976¹ by Fergus Wood, a hydrologist with NOAA. Nolle explained in 2011 that he based calculations on 90% of the difference in lunar apsis extremes for the solar year. In other words, a full or new moon is considered a supermoon if ld_s \leq ld_p + 0.1 * (ld_a - ld_p) , where ld_s is the lunar distance at syzygy, ld_a is the lunar distance at the greatest apogee of the year, and ld_p is the lunar distance at the smallest perigee of the year. In practice, there is no official or even consistent definition of how near perigee the full Moon must occur to receive the supermoon label, and new moons rarely receive a supermoon label. Different sources give different definitions. The term perigee-syzygy or perigee full / new moon is preferred in the scientific community. Perigee is the point at which the Moon is closest in its orbit to the Earth, and syzygy is when the Earth, the Moon and the Sun are aligned, which happens at every full or new moon. Fred Espenak uses Nolle's definition but preferring the label of full Moon at perigee, and using the apogee and perigee nearest in time rather than the greatest and least of the year. Wood used the definition of a full or new moon occurring within 24 hours of perigee and also used the label perigee-syzygy. Wood also coined the less-used term proxigee where perigee and the full or new moon are separated by 10 hours or less. Nolle has also added the concept of extreme supermoon in 2000 describing the concept as any new or full moons that are at "100% or greater of the mean perigee".

Occurrence

Of the possible 12 or 13 full (or new) moons each year, usually three or four may be classified as supermoons, as commonly defined. The full moon occurred Thursday December 4, 2025 at 3:14 PST, following an occurrence on November 5, 2025. Due to the event occurring in December it is usually called the "cold moon". The full moon rises on the 4th and 5th of December, Thursday and Friday Evening. The supermoon of November 14, 2016, was the closest full occurrence since January 26, 1948, and will not be surpassed until November 25, 2034. The closest full supermoon of the 21st century will occur on December 6, 2052. The oscillating nature of the distance to the full or new moon is due to the difference between the synodic month and anomalistic months. The period of this oscillation is about 14 synodic months, which is close to 15 anomalistic months. Thus every 14 lunations there is a full moon nearest to perigee. Occasionally, a supermoon coincides with a total lunar eclipse. The most recent occurrence of this by any definition was in May 2022, and the next occurrence will be in October 2033. In the Islamic calendar (a lunar calendar), the occurrence of full supermoons follows a cycle. In the first year, the full moon is near perigee in month 1 or 2, the next year in month 3 or 4, and so on. In the seventh year of the cycle the full moons are never very near to perigee. Approximately every 20 years the occurrences move to one month earlier. such a transition is occurring, so full supermoons occur twice in succession. For example in year 1446, they occur both in month 3 ( , on September 18, 2024) and in month 4 ( , on October 17, 2024).

Appearance

A full moon at perigee appears roughly 14% larger in diameter than at apogee. Many observers insist that the Moon looks bigger to them. This is likely due to observations shortly after sunset when the Moon appears near the horizon and the Moon illusion is at its most apparent. While the Moon's surface luminance remains the same, because it is closer to the Earth the is about 30% brighter than at its farthest point, or apogee. This is due to the inverse square law of light, which changes the amount of light received on Earth in inverse proportion to the distance from the Moon. But, the perceived brightness will be the same; the Moon will just be smaller in one's field of view. That change in size is exactly proportional to the change in the amount of light. A supermoon directly overhead could provide up to .

See also

Notes

References

External links

Lunar Apogee/Perigee Calculator at Fourmilab Richard Nolle's definition Richard Nolle's list of supermoons in the 21st century Full Moon at Perigee (Super Moon): 2001 to 2100 by Fred Espenak Supermoons and Micromoons Next Supermoons

Text derived from https://en.wikipedia.org/w/index.php?oldid=1363499249 under CC BY-SA 4.0; modifications have been made.