September equinox


The September 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.
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 in the Northern Hemisphere, while marking the end of astronomical winter and the start of astronomical spring in the Southern Hemisphere.

Occurrences

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 that occur from the year 2018 to 2028 are listed as follows:
Datetime
September 23, 201801:54
September 23, 201907:50
September 22, 202013:31
September 22, 202119:21
September 23, 202201:04
September 23, 202306:50
September 22, 202412:44
September 22, 202518:19
September 23, 202600:05
September 23, 202706:02
September 22, 202811:45

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 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" of a little under a half 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

Judaism

  • The Jewish Sukkot usually falls on the first full moon after the northern hemisphere autumnal equinox, although occasionally it will occur on the second full moon.
  • Rosh Hashanah falls on a new moon close to this equinox, although occasionally it will occur on the second full moon.

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 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

Americas