Full moon

The supermoon of 14 November 2016 was 356,511 km (221,526 mi) away[1] from the center of Earth, the closest occurrence since 1948. It will not be closer again until 2034.[2]
The full Moon as viewed through a 235 mm (9.25 in) Schmidt-Cassegrain telescope. The Moon was near its northernmost ecliptic latitude, so the southern craters are especially prominent.
The full Moon during the total lunar eclipse of 31 January 2018

The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (more exactly, when the ecliptic longitudes of the Sun and Moon differ by 180°). This means that the lunar hemisphere facing Earth – the near side – is completely sunlit and appears as a circular disk, while the far side is dark. The full moon occurs once roughly every month.

When the Moon moves into Earth's shadow, a lunar eclipse occurs, during which all or part of the Moon's face may appear reddish due to the Rayleigh scattering of blue wavelengths and the refraction of sunlight through Earth's atmosphere.[3][4][5] Lunar eclipses happen only during full moon and around points on its orbit where the satellite may pass through the planet's shadow. A lunar eclipse does not occur every month because the Moon's orbit is inclined 5.14° with respect to the ecliptic plane of Earth; thus, the Moon usually passes north or south of Earth's shadow, which is mostly restricted to this plane of reference. Lunar eclipses happen only when the full moon occurs around either node of its orbit (ascending or descending). Therefore, a lunar eclipse occurs approximately every 6 months and often 2 weeks before or after a solar eclipse, which occurs during new moon around the opposite node.

The interval period between a new or full moon and the next same phase, a synodic month, averages about 29.53 days. Therefore, in those lunar calendars in which each month begins on the day of the new moon, the full moon falls on either the 14th or 15th day of the lunar month. Because a calendar month consists of a whole number of days, a lunar month may be either 29 or 30 days long.

Characteristics

A full moon is often thought of as an event of a full night's duration. This is somewhat misleading because its phase seen from Earth continuously waxes or wanes (though much too slowly to notice in real time with the naked eye). Its maximum illumination occurs at the moment waxing has stopped. For any given location, about half of these maximum full moons may be visible, while the other half occurs during the day, when the full moon is below the horizon.

Many almanacs list full moons not only by date, but also by their exact time, usually in Coordinated Universal Time (UTC). Typical monthly calendars that include lunar phases may be offset by one day when used in a different time zone.

Full moon is generally a suboptimal time to conduct astronomical observations because the bright sunlight reflected by the Moon then outshines the apparently dimmer stars.

On 12 December 2008, the full moon occurred closer to the Earth than it had been at any time for the previous 15 years, called a supermoon.[6]

On 19 March 2011, another full supermoon occurred, closer to the Earth than at any time for the previous 18 years.[7]

On 14 November 2016, a full supermoon occurred closer to the Earth than at any time for the previous 68 years.[8]

Formula

The date and approximate time of a specific full moon (assuming a circular orbit) can be calculated from the following equation:[9]

${\displaystyle d=20.362000+29.530588861\times N+102.026\times 10^{-12}\times N^{2}}$

where d is the number of days since 1 January 2000 00:00:00 in the Terrestrial Time scale used in astronomical ephemerides; for Universal Time (UT) add the following approximate correction to d:

${\displaystyle -0.000739-(235\times 10^{-12})\times N^{2}}$ days

where N is the number of full moons since the first full moon of 2000. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moon's orbit.[10] See New moon for an explanation of the formula and its parameters.

The age and apparent size of the full moon vary in a cycle of just under 14 synodic months, which has been referred to as a full moon cycle.

Other Languages
Afrikaans: Volmaan
asturianu: Lluna enllena
বাংলা: পূর্ণিমা
Bân-lâm-gú: Goe̍h-îⁿ
български: Пълнолуние
català: Lluna plena
čeština: Úplněk
dansk: Fuldmåne
Deutsch: Vollmond
Ελληνικά: Πανσέληνος
español: Plenilunio
Esperanto: Plenluno
فارسی: بدر (ماه)
français: Pleine lune
galego: Plenilunio
한국어: 보름달
Bahasa Indonesia: Bulan purnama
italiano: Plenilunio
ქართული: სავსე მთვარე
kaszëbsczi: Pełniô
Kiswahili: Mwezi mpevu
Kreyòl ayisyen: Plèn lin
kurdî: Heyva tijî
Latina: Luna plena
Lëtzebuergesch: Vollmound
lietuvių: Pilnatis
മലയാളം: പൗർണ്ണമി
Bahasa Melayu: Bulan purnama
မြန်မာဘာသာ: လပြည့်
नेपाली: पूर्णिमा

norsk: Fullmåne
occitan: Luna plena
ਪੰਜਾਬੀ: ਪੂਰਨਮਾਸ਼ੀ
Plattdüütsch: Vullmaand
polski: Pełnia
português: Lua cheia
Ripoarisch: Vollmond
română: Lună plină
Runa Simi: Killapura
русский: Полнолуние
Scots: Full muin
සිංහල: පසළොස්වක
slovenčina: Spln
suomi: Täysikuu
svenska: Fullmåne
தமிழ்: பூரணை
తెలుగు: పౌర్ణమి
тоҷикӣ: Бадр (моҳ)
Türkçe: Dolunay
українська: Повний Місяць
vepsän kel’: Täuz'kudan'
Tiếng Việt: Trăng tròn