New moon
Overview
 
In astronomical terminology, the new moon is the lunar phase
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

 that occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, in its monthly orbital motion around Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, lies between Earth and the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, and is therefore in conjunction with the Sun as seen from Earth. At this time, the dark (unilluminated) portion of the Moon faces almost directly toward Earth, so that the Moon is not visible to the naked eye.

The original meaning of the phrase new moon was the first visible crescent
Crescent
In art and symbolism, a crescent is generally the shape produced when a circular disk has a segment of another circle removed from its edge, so that what remains is a shape enclosed by two circular arcs of different diameters which intersect at two points .In astronomy, a crescent...

 of the Moon, after conjunction with the Sun.
Encyclopedia
In astronomical terminology, the new moon is the lunar phase
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

 that occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, in its monthly orbital motion around Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, lies between Earth and the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, and is therefore in conjunction with the Sun as seen from Earth. At this time, the dark (unilluminated) portion of the Moon faces almost directly toward Earth, so that the Moon is not visible to the naked eye.

The original meaning of the phrase new moon was the first visible crescent
Crescent
In art and symbolism, a crescent is generally the shape produced when a circular disk has a segment of another circle removed from its edge, so that what remains is a shape enclosed by two circular arcs of different diameters which intersect at two points .In astronomy, a crescent...

 of the Moon, after conjunction with the Sun. This takes place over the western horizon
Horizon
The horizon is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. At many locations, the true horizon is obscured by trees, buildings, mountains, etc., and the resulting...

 in a brief period between sunset and moonset, and therefore the precise time and even the date of the appearance of the new moon by this definition will be influenced by the geographical location of the observer. The astronomical new moon, sometimes known as the dark moon
Dark moon
A dark moon describes the Moon during that time that it is invisible against the backdrop of the Sun in the sky. The duration of a dark moon is between 1.5 and 3.5 days, depending on the orientation of the Earth and Sun....

to avoid confusion, occurs by definition at the moment of conjunction in ecliptic longitude with the Sun, when the Moon is invisible from the Earth. This moment is unique and does not depend on location, and in certain circumstances it coincides with a solar eclipse
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...

.

The new moon in its original meaning of first crescent marks the beginning of the month in lunar calendar
Lunar calendar
A lunar calendar is a calendar that is based on cycles of the lunar phase. A common purely lunar calendar is the Islamic calendar or Hijri calendar. A feature of the Islamic calendar is that a year is always 12 months, so the months are not linked with the seasons and drift each solar year by 11 to...

s such as the Muslim calendar
Islamic calendar
The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

, and in lunisolar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

s such as the Hebrew calendar
Hebrew calendar
The Hebrew calendar , or Jewish calendar, is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah portions, yahrzeits , and daily Psalm reading, among many ceremonial uses...

, Hindu calendar
Hindu calendar
The hindu calendar used in ancient times has undergone many changes in the process of regionalization, and today there are several regional Indian calendars, as well as an Indian national calendar. Nepali calendar, Bengali calendar, Malayalam calendar, Tamil calendar, Telugu calendar, Kannada...

s, and Buddhist calendar
Buddhist calendar
The Buddhist calendar is used on mainland Southeast Asia in the countries of Thailand, Cambodia, Laos, Burma and Sri Lanka in several related forms. It is a lunisolar calendar having months that are alternately 29 and 30 days, with an intercalated day and a 30-day month added at regular intervals...

. But in the Chinese calendar
Chinese calendar
The Chinese calendar is a lunisolar calendar, incorporating elements of a lunar calendar with those of a solar calendar. It is not exclusive to China, but followed by many other Asian cultures as well...

, the beginning of the month is marked by the dark moon.

Religious use

  • The Islamic calendar
    Islamic calendar
    The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

     has retained an observational definition of the new moon, marking the new month when the first crescent moon is actually seen, and making it impossible to be certain in advance of when a specific month will begin (in particular, the exact date on which Ramadan
    Ramadan (calendar month)
    Ramadan is the ninth month of the Islamic calendar, and the month in which the Quran was revealed.Ramadan is the holiest of months in the Islamic calendar, and fasting in this month is one of the Five Pillars of Islam. The month is spent by Muslims fasting during the daylight hours from dawn to...

     will begin is not known in advance). In Saudi Arabia
    Saudi Arabia
    The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...

    , if the weather is cloudy when the new moon is expected, observers are sent up in airplanes. In Pakistan
    Pakistan
    Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

    , there is a "Central Ruet-e-Hilal Committee" consisting of ulama
    Ulama
    -In Islam:* Ulema, also transliterated "ulama", a community of legal scholars of Islam and its laws . See:**Nahdlatul Ulama **Darul-uloom Nadwatul Ulama **Jamiatul Ulama Transvaal**Jamiat ul-Ulama -Other:...

     (religious scholars), which takes help from 150 observatories of the Pakistan Meteorological Department
    Pakistan Meteorological Department
    The Pakistan Meteorological Department, also known as Pak Met Office, is a Government of Pakistan organization which works under the Ministry of Defence...

     all over the country and announces the decision of sighting of new moon. In Iran
    Iran
    Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

     a special committee receives observations of every new moon to determine the beginning of each month. This committee uses one hundred groups of observers.

An attempt to unify Muslims on a scientifically calculated worldwide calendar was adopted by both the Fiqh Council of North America
Fiqh Council of North America
The Fiqh Council of North America is an association of Muslims who interpret Islamic law on the North American continent.Its 18 members issue religious rulings, resolve disputes, and answer questions relating to the Islamic faith...

 and the European Council for Fatwa and Research
European Council for Fatwa and Research
The European Council for Fatwa and Research is a Dublin-based private foundation, founded in London on 29 March - 30 March 1997 on the initiative of the Federation of Islamic Organisations in Europe...

 in 2007. The new calculation requires that conjunction occur before sunset in Mecca, Saudi Arabia and that moon set on the following day must take place after sunset. These can be precisely calculated and therefore a unified calendar is imminent if it becomes adopted worldwide.

  • The new moon is quite significant in Hindu
    Hindu
    Hindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...

     calendar. People generally wait for new moon to start new works. Waxing period of moon is considered good for all good works. Fifteen Moon dates each for waxing and waning period are there. Fifteen dates are classified in five categories, namely Nanda, Bhadra, Jaya, Rikta and Purna and three rotations of these five categories are there. The category rotation starts from first date of moon ending at fifth date and then starting at sixth date and so on. Nanda dates come on First, Sixth and Eleventh moon date, same can be known about others. Nanda dates are good for auspicious works. Bhadra dates can be good for works related with community, social, family, friends. Jaya dates are good where we need to deal with some conflict. Rikta dates are not considered much good and do good for works related with cruelty. Purna dates are good for every work.

  • The new moon is the beginning of the month in the Chinese calendar. Some Buddhist Chinese keep a vegetarian diet on the new moon and full moon each month.

  • The new moon signifies the start of every Jewish month, and is considered an important date and minor holiday
    Rosh Chodesh
    Rosh Chodesh or Rosh ḥodesh is the name for the first day of every month in the Hebrew calendar, marked by the appearance of the new moon. The new moon is marked by the day and hour that the new crescent is observed...

     in the Hebrew calendar
    Hebrew calendar
    The Hebrew calendar , or Jewish calendar, is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah portions, yahrzeits , and daily Psalm reading, among many ceremonial uses...

    . The modern form of the calendar is a rule-based lunisolar calendar
    Lunisolar calendar
    A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

    , akin to the Chinese calendar
    Chinese calendar
    The Chinese calendar is a lunisolar calendar, incorporating elements of a lunar calendar with those of a solar calendar. It is not exclusive to China, but followed by many other Asian cultures as well...

    , measuring months defined in lunar cycles as well as years measured in solar cycles, and distinct from the purely lunar Islamic calendar
    Islamic calendar
    The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

     and the almost entirely solar Gregorian calendar
    Gregorian calendar
    The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

    . According to Jewish tradition, the Jewish calendar is calculated based on mathematical rules handed down from God to Moses at the moment the command was given to make sure that Passover always falls in the springtime. More likely, this fixed lunisolar calendar was introduced by Hillel II
    Hillel II
    Hillel II, also known simply as Hillel held the office of Nasi of the ancient Jewish Sanhedrin between 320 and 385 CE. He was the son and successor of Judah III. He was a Jewish communal and religious authority, circa 330 - 365 CE...

    . This calculation makes use of a mean lunation length used by Ptolemy
    Ptolemy
    Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

     and handed down from Babylonians (see Lunar theory#Babylon), which is still very accurate: ca. 29.530594 days vs. a present value (see below) of 29.530589 days. This difference of only 0.0000005, or five millionths of a day, adds up to about only 4 hours since Babylonian times.

  • The native messianic
    Hebrew Roots
    This article refers to the modern religious movement. For the Hebrew language grammatical structure, see Hebrew rootHebrew Roots is a contemporary global spiritual movement to return to the true faith revealed during the personal earthly ministry of Yeshua the Messiah.Hebrew Roots MovementThe...

     Pentecostal group, the New Israelites of Peru
    Agricultural People's Front of Peru
    The Agricultural People's Front of Peru is a political party in Peru.At the legislative elections of 8 April 2001, the party won 1.7 % of the popular vote and no seats in the Congress of the Republic...

    , keeps the new moon as a Sabbath of rest. As an evangelical church, it follows the Bible's teachings that God sanctified the seventh-day Sabbath, now largely known as Saturday, and the new moons in addition to it. See Ezekiel 46:1, 3. No work may be done from dusk until dusk, and the services run for 11 hours, although a large number spend 24 hours within the gates of the temples, sleeping and singing praises throughout the night.

  • The new moon is also an important event in Wicca
    Wicca
    Wicca , is a modern Pagan religious movement. Developing in England in the first half of the 20th century, Wicca was popularised in the 1950s and early 1960s by a Wiccan High Priest named Gerald Gardner, who at the time called it the "witch cult" and "witchcraft," and its adherents "the Wica."...

    . Some Wiccans celebrate only the full moons and others celebrate both dark and full. The waning phase is a time for turning inward and reflecting. It is a time for reaping what was put forth in the waxing phase of the moon. The waning phase is often used for banishing rituals. The dark moon is a quiet time; a time for divination and personal workings. The dark moon is a time for holding power.

  • The new moon is also important in astrology
    Astrology
    Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...

    , as is the full moon
    Full moon
    Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

    .

Determining new moons: an approximate formula

The time interval between new moons—a lunation—is variable. The mean time between new moons, the synodic month, is about 29.53... days. An approximate formula to compute the mean moments of new moon (conjunction between Sun and Moon) for successive months is:


where N is an integer, starting with 0 for the first new moon in the year 2000, and that is incremented by 1 for each successive synodic month; and the result d is the number of days (and fractions) since 2000-01-01 00:00:00 reckoned in the time scale known as Terrestrial Time
Terrestrial Time
Terrestrial Time is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of the Earth....

 (TT) used in ephemerides.

To obtain this moment expressed in Universal Time
Universal Time
Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...

 (UT, world clock time), add the result of following approximate correction to the result d obtained above:
days


Periodic perturbations change the time of true conjunction from these mean values. For all new moons between 1601 and 2401, the maximum difference is 0.592 days = 14h13m in either direction. The duration of a lunation (i.e. the time from new moon to the next new moon) varies in this period between 29.272 and 29.833 days, i.e. −0.259d = 6h12m shorter, or +0.302d = 7h15m longer than average. This range is smaller than the difference between mean and true conjunction, because during one lunation the periodic terms cannot all change to their maximum opposite value.

See the article on the full moon cycle
Full moon cycle
The full moon cycle is a cycle of about 14 lunations over which full moons vary in apparent size and age . The sequence is*Full moon big - *Full moon young -...

 for a fairly simple method to compute the moment of new moon more accurately.

The long-term error of the formula is approximately: 1 cy2 seconds in TT, and 11 cy2 seconds in UT (cy is centuries since 2000; see section Explanation of the formulae for details.)

Explanation of the formula

The moment of mean conjunction can easily be computed from an expression for the mean ecliptic longitude of the Moon minus the mean ecliptic longitude of the Sun (Delauney parameter D). Jean Meeus
Jean Meeus
Jean Meeus is a Belgian astronomer specializing in celestial mechanics. The asteroid 2213 Meeus is named after him.Jean Meeus studied mathematics at the University of Leuven in Belgium, where he received the Degree of Licentiate in 1953...

 gave formulae to compute this in his popular Astronomical Formulae for Calculators based on the ephemerides of Brown and Newcomb (ca. 1900); and in his 1st edition of Astronomical Algorithms based on the ELP2000-85 (the 2nd edition uses ELP2000-82 with improved expressions from Chapront et al. in 1998). These are now outdated: Chapront et al. (2002) published improved parameters. Also Meeus's formula uses a fractional variable to allow computation of the four main phases, and uses a second variable for the secular terms. For the convenience of the reader, the formula given above is based on Chapront's latest parameters and expressed with a single integer variable, and the following additional terms have been added:

constant term:
  • Like Meeus, apply the constant terms of the aberration of light
    Aberration of light
    The aberration of light is an astronomical phenomenon which produces an apparent motion of celestial objects about their real locations...

     for the Sun and light-time correction
    Light-time correction
    Light-time correction is a displacement in the apparent position of a celestial object from its true position caused by the object's motion during the time it takes its light to reach an observer....

     for the Moon to obtain the apparent difference in ecliptic longitudes:

Sun: +20.496"

Moon: −0.704"

Correction in conjunction: −0.000451 days.

  • For UT: at 1 January 2000, ΔT
    Delta T
    ΔT, Delta T, delta-T, deltaT, or DT is the time difference obtained by subtracting Universal Time from Terrestrial Time : ΔT=TT−UT....

     (= TT
    Terrestrial Time
    Terrestrial Time is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of the Earth....

     − UT
    Universal Time
    Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...

     ) was +63.83 s; hence the correction for the clock time UT = TT − ΔT of the conjunction is:

−0.000739 days.


quadratic term:
  • In ELP2000–85 (see Chapront et alii 1988), D has a quadratic term of −5.8681"T2; expressed in lunations N, this yields a correction of +87.403N2. days to the time of conjunction. The term includes a tidal contribution
    Tidal acceleration
    Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite , and the primary planet that it orbits . The "acceleration" is usually negative, as it causes a gradual slowing and recession of a satellite in a prograde orbit away from the primary, and a corresponding...

     of 0.5×(−23.8946 "/cy2). The most current estimate from Lunar Laser Ranging for the acceleration is (see Chapront et alii 2002): (−25.858 ±0.003)"/cy2. Therefore the new quadratic term of D is = -6.8498"T2 Indeed the polynomial provided by Chapront et alii (2002) provides the same value (their Table 4). This translates to a correction of +14.622N2 days to the time of conjunction; the quadratic term now is:

+102.026N2 days.

  • For UT: analysis of historical observations show that ΔT has a long-term increase of +31 s/cy2. Converted to days and lunations; the correction from ET to UT becomes:

−235N2 days.


The theoretical tidal contribution to ΔT is about +42 s/cy2. the smaller observed value is thought to be mostly due to changes in the shape of the Earth Because the discrepancy is not fully explained, uncertainty of our prediction of UT (rotation angle of the Earth) may be as large as the difference between these values: 11 s/cy2. The error in the position of the Moon itself is only maybe 0.5"/cy2, or (because the apparent mean angular velocity of the Moon is about 0.5"/s), 1 s/cy2 in the time of conjunction with the Sun.

See also

  • Black moon
    Black moon
    In astronomy, the term black moon is neither well-known nor frequently used. As a consequence it has no accepted definition, but seems to have occasionally been applied to at least four different situations:-Other names:...

  • Blue moon
    Blue moon
    A blue moon can refer to the third full moon in a season with four full moons. Most years have twelve full moons that occur approximately monthly. In addition to those twelve full lunar cycles, each solar calendar year contains roughly eleven days more than the lunar year of 12 lunations...

  • Ecclesiastical new moon
    Ecclesiastical new moon
    An ecclesiastical new moon is the first day of a lunar month in an ecclesiastical lunar calendar. Such months have a whole number of days, 29 or 30, whereas true synodic months can vary from about 29.27 to 29.83 days in length. Medieval authors equated the ecclesiastical new moon with a new...

  • Full moon
    Full moon
    Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

  • Half moon
    Half Moon
    Half Moon is a lunar phase coinciding with neap tides, which are often easier for seafarers than spring tides. This would apply to the first quarter and last quarter moon; in both cases, half of the moon's disk is lit...

  • Metonic cycle
    Metonic cycle
    In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

  • Lunar Cycle

External links

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