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autumnal equinox, two moments in the year when the Sun is exactly above the Equator and day and night are of equal length; also, either of the two points in the sky where the ecliptic (the Sun’s annual pathway) and the celestial equator intersect.
In the Northern Hemisphere, the March equinox is called the vernal or spring equinox while the September equinox is called the autumnal or fall equinox. In the Southern Hemisphere, the reverse is true. During the year, equinoxes alternate with solstices. Leap years and other factors cause the dates of both events to vary slightly. [12]
According to the astronomical definition, fall begins with the autumnal equinox. In the Northern Hemisphere, it's the September equinox; south of the equator, it is the equinox in March. What is an equinox? Equinoxes and solstices in your city. Autumn Equinox, Northern Hemisphere (September) North America, Europe, most of Asia, Northern Africa.
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 the start of astronomical spring (vernal equinox) in the Southern Hemisphere.
The March and September equinoxes mark the beginning of the spring and autumn seasons on Earth, according to one definition. The equinox in September is the start of fall in the Northern Hemisphere and the beginning of spring south of the equator.
Sep 20, 2016 · Autumnal Equinox and Other Sky Events: What You Need to Know. Find out what an equinox is and how the day is linked to the reason for the seasons.
The 2025 September equinox will fall at 18:20 UTC (1:20 p.m. CDT) on September 22, 2024. On this day, days and nights are approximately (but not exactly) equal in length for everyone across the...
