The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth . By extension, it is also a plane of reference in the equatorial coordinate system . In other words, the celestial equator is an abstract projection of the terrestrial equator into outer space . Due to Earth's axial tilt , the celestial equator is currently inclined by about 23.44° with respect to the ecliptic (the plane of Earth's orbit ), but has varied from about 22.0° to 24.5° over the past 5 million years due to perturbation from other planets.
11-759: (Redirected from Autumn Equinox ) Autumnal equinox or variations, may refer to: September equinox , the autumnal equinox in the Northern Hemisphere March equinox , the autumnal equinox in the Southern Hemisphere Other uses [ edit ] Autumnal Equinox Day (Japanese: 秋分の日, Shūbun no Hi ), a public holiday in September in Japan Autumn Equinox: Amethyst Deceivers ,
22-522: A 1998 record by Coil "An Autumnal Equinox", a song from The Caretaker's 2016 album Everywhere at the End of Time - Stage 1 See also [ edit ] All pages with titles containing Autumn equinox All pages with titles containing Autumnal equinox Equinox (disambiguation) Autumn (disambiguation) Winter solstice (disambiguation) Summer solstice (disambiguation) Spring equinox (disambiguation) Topics referred to by
33-455: Is different from Wikidata All article disambiguation pages All disambiguation pages September 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. At
44-507: 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. 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
55-425: The zenith , the point directly overhead. As the observer moves north (or south), the celestial equator tilts towards the opposite horizon . The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth. At the poles , the celestial equator coincides with
66-555: 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. The September equinox marked the first day of the French Republican Calendar . Celestial equator An observer standing on Earth's equator visualizes the celestial equator as a semicircle passing through
77-488: The astronomical horizon. At all latitudes , the celestial equator is a uniform arc or circle because the observer is only finitely far from the plane of the celestial equator, but infinitely far from the celestial equator itself. Astronomical objects near the celestial equator appear above the horizon from most places on earth, but they culminate (reach the meridian) highest near the equator. The celestial equator currently passes through these constellations : These are
88-540: 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
99-411: 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
110-429: The same term [REDACTED] This disambiguation page lists articles associated with the title Autumnal equinox . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Autumnal_equinox&oldid=1161252519 " Category : Disambiguation pages Hidden categories: Short description
121-561: The start of astronomical spring (vernal equinox) in the Southern Hemisphere . 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 (UTC) are listed as follows: The point where the Sun crosses the celestial equator southwards is called the First Point of Libra . However, because of
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