March equinox


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Related to March equinox: September equinox, June solstice

March equinox

[′märch ′ē·kwə‚näks]
(astronomy)

vernal equinox

vernal equinoxclick for a larger image
i. That point of intersection of the ecliptic and the celestial equator occupied by the sun as it changes from a south to a north declination, on or about March 21. Also called the March equinox or the first point of Aries.
ii. That instant the sun reaches the point of zero declination when crossing the celestial equator from south to north.

equinox

equinoxclick for a larger image
Positions of sun and the earth at spring and autumnal equinoxes.
i. One of the two points of intersection of the ecliptic and the celestial equators, occupied by the sun when its declination is 0°. Also called an equinoctial point. That point occupied on or about March 21, when the sun's declination changes from south to north, is called the vernal equinox, spring equinox, March equinox, or first point of Aries that point occupied on or about September 23, when the declination changes from north to south, is called the autumnal equinox, September equinox, or first point of Libra. Equinox is often used to mean vernal equinox, when referring to the origin of measurement of right ascension and celestial longitude. At the time of equinox, the duration of day and night is the same or equal.
ii. That instant the sun occupies one of the equinoctial points.
References in periodicals archive ?
The March equinox was one of the most important dates in ancient Egyptian and Persian calendars.
So during one visibility period of Saturn we can see the shadows moving from west to east and from either north to south (around the March equinox on Saturn) or south to north (around the September equinox).
The 2009 March equinox on Saturn is now behind us, and during the next years we will see the rings opening until the planet reaches its June solstice in 2017.
Many consider the earthly Groundhog Day a celestial holiday with roots in science, given that it takes place during the time in the Earth's orbit around the Sun when we move between the December solstice and the March equinox.