September equinox

Last updated

UT date and time of
equinoxes and solstices on Earth [1] [2]
event equinox solstice equinox solstice
monthMarch [3] June [4] September [5] December [6]
yeardaytimedaytimedaytimedaytime
20192021:582115:542307:502204:19
20202003:502021:432213:312110:03
20212009:372103:322219:212115:59
20222015:332109:142301:042121:48
20232021:252114:582306:502203:28
20242003:072020:512212:442109:20
20252009:022102:422218:202115:03
20262014:462108:252300:062120:50
20272020:252114:112306:022202:43
20282002:172020:022211:452108:20
20292008:012101:482217:372114:14
Illumination of Earth by the Sun on the day of an equinox Earth-lighting-equinox EN.png
Illumination of Earth by the Sun on the day of an equinox

The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur from September 21 to 24.

Contents

At the equinox, the Sun as viewed from the equator rises due east and sets due west. Before the Southward equinox, the Sun rises and sets more northerly, and afterwards, it rises and sets more southerly.

The equinox may be taken to mark the end of astronomical summer and the beginning of astronomical autumn (autumnal equinox) in the Northern Hemisphere, while marking the end of astronomical winter and the start of astronomical spring (vernal equinox) in the Southern Hemisphere. [7]

Occurrences

Sunset at the equinox from the site of Pizzo Vento at Fondachelli Fantina, Sicily Equinozio da Pizzo Vento,tramonto fondachelli fantina, sicilia.JPG
Sunset at the equinox from the site of Pizzo Vento at Fondachelli Fantina, Sicily

The September equinox is one point in time commonly used to determine the length of the tropical year.

The dates and times of the September equinoxes [8] that occur from the year 2018 to 2028 (UTC) are listed as follows:

Datetime (UTC)
2018-09-2301:54
2019-09-2307:50
2020-09-2213:31
2021-09-2219:21
2022-09-2301:04
2023-09-2306:50
2024-09-2212:44
2025-09-2218:19
2026-09-2300:05
2027-09-2306:02
2028-09-2211:45

Constellation

The point where the Sun crosses the celestial equator southwards is called the First Point of Libra. However, because of the precession of the equinoxes, this point is no longer in the constellation Libra, but rather in Virgo.

The solar point of the September equinox passed from Libra and into Virgo in −729 (730 BCE) and will enter Leo in 2439.

Apparent movement of the Sun in relation to the horizon

At the equinox, the Sun rises directly in the east and sets directly in the west. However, because of refraction it will usually appear slightly above the horizon at the moment when its "true" middle is rising or setting. For viewers at the north or south poles, it moves virtually horizontally on or above the horizon, not obviously rising or setting apart from the movement in "declination" (and hence altitude) of a little under a half (0.39) degree per day.

For observers in either hemisphere not at the poles, the Sun rises and sets more and more to the south during the 3 months following the September equinox. This period is the second half of a 6-month long southerly movement, beginning with the June solstice when the Sun rises and sets at its most northern point.

Culture

Calendars

The September equinox marked the first day of the French Republican Calendar.

Commemorations

West Asia

East Asia

  • In Japan Autumnal Equinox Day (秋分の日, Shūbun no hi) is a public holiday. [9] Higan (お彼岸) is a Buddhist holiday exclusively celebrated by Japanese sects during both the Spring and Autumnal Equinox.
  • In Korea, Chuseok is a major harvest festival and a three-day holiday celebrated around the Autumn Equinox.
  • The Mid-Autumn Festival is celebrated on the 15th day of the 8th lunar month, often near the autumnal equinox day, and is an official holiday in mainland China, Hong Kong, Taiwan and in many countries with a significant Chinese minority. As the lunar calendar is not synchronous with the Gregorian calendar, this date could be anywhere from mid-September to early October.
  • The traditional East Asian calendars divide a year into 24 solar terms (节气, literally "climatic segments"), and the autumnal equinox ( Qiūfēn , Chinese and Japanese : 秋分; Korean : 추분; Vietnamese : Thu phân) marks the middle of the autumn season. In this context, the Chinese character 分 means "(equal) division" (within a season).

Judaism

  • The Jewish Sukkot usually falls on the first full moon after the northern hemisphere autumnal equinox, although occasionally (In the modern Jewish calendar, three times every 19 years) it will occur on the second full moon.
  • Rosh Hashanah falls on a new moon close to this equinox.

Europe

  • Dożynki is a Slavic harvest festival. In pre-Christian times the feast usually fell on the autumn equinox.
  • The Southward equinox was "New Year's Day" in the French Republican Calendar, which was in use from 1793 to 1805. The French First Republic was proclaimed and the French monarchy was abolished on September 21, 1792, making the following day (the equinox day that year) the first day of the "Republican Era" in France. The start of every year was to be determined by astronomical calculations following the real Sun and not the mean Sun.
  • The traditional harvest festival in the United Kingdom was celebrated on the Sunday of the full moon closest to the September equinox.

Neopaganism

  • Neopagans observe the September equinox as a cardinal point on the Wheel of the Year. In the Northern Hemisphere some varieties of paganism adapt Autumn Equinox traditions. In the Southern Hemisphere, the vernal equinox corresponds with Ostara.

Americas

See also

Related Research Articles

A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September.

A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20-22 June and 20-22 December. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes.

<span class="mw-page-title-main">First point of Aries</span> Point on the celestial sphere

The first point of Aries, also known as the cusp of Aries, is the location of the March equinox, used as a reference point in celestial coordinate systems. In diagrams using such coordinate systems, it is often indicated with the symbol ♈︎. Named for the constellation of Aries, it is one of the two points on the celestial sphere at which the celestial equator crosses the ecliptic, the other being the first point of Libra, located exactly 180° from it. Due to precession of the equinoxes since the positions were originally named in antiquity, the position of the Sun when at the March equinox is now in Pisces; when it is at the September equinox, it is in Virgo.

Autumnal Equinox Day is a public holiday in Japan that usually occurs on September 22 or 23, the date of Southward equinox in Japan Standard Time. Due to the necessity of recent astronomical measurements, the date of the holiday is not officially declared until February of the previous year. Autumnal Equinox Day became a public holiday in 1948. In 1947 and before, it was the date of Shūki kōreisai (秋季皇霊祭), an event relating to Shinto. Like other holidays, this holiday was repackaged as a non-religious holiday for the sake of separation of religion and state in Japan's postwar constitution.

Vernal Equinox Day is a public holiday in Japan that occurs on the date of the Northward equinox in Japan Standard Time, usually March 20 or 21. The date of the holiday is not officially declared until February of the previous year, due to the need for recent astronomical measurements.

<span class="mw-page-title-main">Spring (season)</span> One of the Earths four temperate seasons

Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures and customs. When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere and vice versa. At the spring equinox, days and nights are approximately twelve hours long, with daytime length increasing and nighttime length decreasing as the season progresses until the Summer Solstice in June and December.

<span class="mw-page-title-main">Twilight</span> Atmospheric illumination by the Sun below the horizon

Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs.

<span class="mw-page-title-main">Timber circle</span> Rings of upright wooden posts

In archaeology, timber circles are rings of upright wooden posts, built mainly by ancient peoples in the British Isles and North America. They survive only as gapped rings of post-holes, with no evidence they formed walls, making them distinct from palisades. Like stone circles, it is believed their purpose was ritual, ceremonial, and/or astronomical. Sometimes in North America they are referred to as woodhenge.

<span class="mw-page-title-main">March equinox</span> When sun appears directly over equator

The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox in the Northern Hemisphere and as the autumnal equinox in the Southern Hemisphere.

The term Uttarāyaṇa is derived from two different Sanskrit words – "uttaram" (North) and "ayanam" (movement) – thus indicating the northward movement of the Sun. In the Gregorian calendar, this pertains to the "actual movement of the sun with respect to the earth." Also known as the six month period that occurs between the winter solstice and summer solstice. According to the Indian solar calendar, it refers to the movement of the Sun through the zodiac. This difference is because the solstices continually precess at a rate of 50 arcseconds per year due to the precession of the equinoxes, i.e. this difference is the difference between the sidereal and tropical zodiacs. The Surya Siddhanta bridges this difference by juxtaposing the four solstitial and equinoctial points with four of the twelve boundaries of the rashis.

<span class="mw-page-title-main">Winter solstice</span> Astronomical phenomenon

The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere. For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, and when the Sun is at its lowest daily maximum elevation in the sky. Each polar region experiences continuous darkness or twilight around its winter solstice. The opposite event is the summer solstice.

<span class="mw-page-title-main">Summer solstice</span> Astronomical phenomenon

The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the summer solstice is the day with the longest period of daylight and shortest night of the year, when the Sun is at its highest position in the sky. At either pole there is continuous daylight at the time of its summer solstice. The opposite event is the winter solstice.

<span class="mw-page-title-main">June solstice</span> Annual solstice between 20 and 22 June

The June solstice is the solstice on Earth that occurs annually between 20 and 22 June according to the Gregorian calendar. In the Northern Hemisphere, the June solstice is the summer solstice, while in the Southern Hemisphere it is the winter solstice. It is also known as the northern solstice. During June solstice, the Sun is directly over the Tropic of Cancer, located in the northern hemisphere.

<span class="mw-page-title-main">December solstice</span> Annual solstice on 20–22 December

The December solstice, also known as the southern solstice, is the solstice that occurs each December – typically on 21 December, but may vary by one day in either direction according to the Gregorian calendar. In the Northern Hemisphere, the December solstice is the winter solstice, whilst in the Southern Hemisphere it is the summer solstice. During December solstice, the Sun is directly over the Tropic of Capricorn, located in the Southern Hemisphere.

A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations, and as such there are a number of both modern and historical cultures whose number of seasons varies.

<span class="mw-page-title-main">Cahokia Woodhenge</span> Series of timber circles at the Cahokia archaeologial site, US

The Cahokia Woodhenge was a series of large timber circles located roughly 850 metres (2,790 ft) to the west of Monks Mound at the Mississippian culture Cahokia archaeological site near Collinsville, Illinois, United States. They are thought to have been constructed between 900 and 1100 CE, with each one being larger and having more posts than its predecessor. The site was discovered as part of salvage archaeology in the early 1960s interstate highway construction boom, and one of the circles was reconstructed in the 1980s. The circle has been used to investigate archaeoastronomy at Cahokia. Annual equinox and solstice sunrise observation events are held at the site.

Autumnal equinox or variations, may refer to:

Spring equinox or vernal equinox or variations may refer to:

Persian astronomy or Iranian astronomy refers to the astronomy in ancient Persian history.

References

  1. Astronomical Applications Department of USNO. "Earth's Seasons - Equinoxes, Solstices, Perihelion, and Aphelion" . Retrieved August 1, 2022.
  2. "Solstices and Equinoxes: 2001 to 2100". AstroPixels.com. February 20, 2018. Retrieved December 21, 2018.
  3. Équinoxe de printemps entre 1583 et 2999
  4. Solstice d’été de 1583 à 2999
  5. Équinoxe d’automne de 1583 à 2999
  6. Solstice d’hiver
  7. "Defining Seasons". Time and Date AS. Retrieved May 31, 2019.
  8. "Solstices & Equinoxes for UTC (Surrounding 10 Years)". www.timeanddate.com. Retrieved October 10, 2021.
  9. "Autumnal Equinox Day (秋分の日): More Than Just a Change of Seasons". cotoacademy.com. September 23, 2017. Retrieved September 22, 2020.
  10. "Visitors Guide to the Woodhenge" . Retrieved December 19, 2017.
  11. Iseminger, William. "Welcome the Fall Equinox at Cahokia Mounds". Illinois Department of Natural Resources. Retrieved December 20, 2017.
  12. "Winter Solstice Sunrise Observance at Cahokia Mounds". Collinsville Chamber of Commerce. Retrieved December 20, 2017.
  13. "Cahokia Mounds Mark Spring Equinox : The keepers of Cahokia Mounds will host a spring gathering to celebrate the vernal equinox". Indian Country Today. Indian Country Media Network . Retrieved December 20, 2017.