autumnal equinox(redirected from First Point of Libra)
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Related to First Point of Libra: Invernal equinox
1. One of two points at which the ecliptic intersects the celestial equator. At the autumnal equinox, the sun is moving along the ecliptic in a southeasterly direction.
2. The moment at which the sun passes through this point on or about September 23, marking the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
1. (Physical Geography) the time at which the sun crosses the plane of the equator away from the relevant hemisphere, making day and night of equal length. It occurs about Sept 23 in the N hemisphere (March 21 in the S hemisphere)
2. (Astronomy) the time at which the sun crosses the plane of the equator away from the relevant hemisphere, making day and night of equal length. It occurs about Sept 23 in the N hemisphere (March 21 in the S hemisphere)
3. (Astronomy) astronomy
a. the point, lying in the constellation Virgo, at which the sun's ecliptic intersects the celestial equator
b. the time at which this occurs as the sun travels north to south (23 September)
1. See under equinox (def. 1).
2. Also called autum′nal point′. the position of the sun at the time of the autumnal equinox.
The moment of the year when the sun crosses the celestial equator while moving from north to south. It occurs on September 22 or 23, marking the beginning of autumn in the Northern Hemisphere. Compare vernal equinox.
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|Noun||1.||autumnal equinox - September 22 |
equinox - either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length
|2.||autumnal equinox - (astronomy) the equinoctial point that lies in the constellation of Virgo|
astronomy, uranology - the branch of physics that studies celestial bodies and the universe as a whole