The September equinox is the equinox which occurs in the month of September. Due to differences between the calendar year and the tropical year, the September equinox can occur at any time from the 22nd to the 24th day of September. It has been suggested that Equinoctial point be merged into this article or section. ... September is the ninth month of the year in the Gregorian Calendar and one of four Gregorian months with 30 days. ... Jump to: navigation, search A calendar is a system for naming periods of time, typically days. ... A tropical year is the length of time that the Sun, as viewed from the Earth, takes to return to the same position along the ecliptic (its path among the stars on the celestial sphere). ...
In the Northern Hemisphere the September equinox is known as the autumnal equinox. In the Southern Hemisphere it is known as the vernal or spring equinox. The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball). On Earth, the Northern Hemisphere contains most of the land and population. ... Illumination of Earth by Sun on the day of equinox In astronomy, the autumnal equinox (fall equinox, September equinox, or southward equinox) signals the beginning of autumn in the northern hemisphere: the moment when the sun appears to cross the celestial equator, heading southward; the equinox occurs around September 22... The Southern Hemisphere of Earth highlighted in yellow. ... Illumination of Earth by Sun on the day of equinox In astronomy, the vernal equinox (spring equinox, March equinox, or northward equinox) is the moment when the sun appears to cross the celestial equator, heading northward. ... Spring is one of the four seasons of temperate zones. ...
The vernal equinox is the beginning of spring; the autumnal equinox is the beginning of autumn.
In astronomy, an equinox is defined the moment when the sun reaches one of two intersections between the ecliptic and the celestial equator.
The March equinox is the vernal equinox in the northern hemisphere and is the autumnal equinox in the southern hemisphere; for the Septemberequinox, those events are interchanged.
The equinoxes then, together with the solstices, are the defining moments of the start of the (astronomical) seasons, except in China, where they mark the center of the respective seasons.
As such the vernal equinox is the equinox where the Sun passes from south to north, and is a zeropoint in some celestial coordinate systems.
The vernal equinox, the one the Sun passes in March on its way from south to north, has a special significance in astronomy as it marks the origin of both ecliptic coordinates and equatorial coordinates, and also the start of the sidereal day.
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