Interesting: Autumnal Equinox
The autumnal equinox is at ecliptic longitude 180° and at right ascension 12h.
In the southern hemisphere, the autumnal equinox corresponds to the center of the Sun crossing the celestial equator moving northward and occurs on the date of the northern vernal equinox.
These two great circles meet at two points, one of which is the vernal equinox and the other the autumnal equinox.
The Autumnal Equinox signals the end of the summer months and the beginning of winter.
The dates of maximum tilt of the Earth’s equator correspond to the Summer Solstice and Winter Solstice, and the dates of zero tilt to the Vernal Equinox and Autumnal Equinox.
At the autumnal equinox , the Sun appears to cross the celestial equator, from north to south; this marks the beginning of autumn in the Northern Hemisphere.
In the United States and the rest of the northern hemisphere, the first day of the autumn season is the day of the year when the Sun crosses the celestial equator moving southward.
An equinox is the moment in time when the centre of the Sun can be observed to be directly above the Earth ’s equator, occurring around March 20 and September 22 each year.
The picture on the left shows the view from the solar system , and from on the surface of the earth.
One of the two places in the sky where the ecliptic crosses the celestial equator; or one of the two times of the year when the Sun crosses these points.
When the Sun passes this point, on about 23 September each year, nights begin to grow longer than days, and continue to do so until the Winter Solstice in December.
In the language of science, an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect.
A common misconception is that the earth is further from the sun in winter than in summer.
In fact, the Sun is at the equator, so both halves of the Earth are getting about the same amount of sunlight.
The dates of maximum tilt of the Earth’s equator correspond to the summer solstice and winter solstice, and the dates of zero tilt to the vernal equinox and autumnal equinox.
The exact date and time of the fall equinox, when the sun moves into the astrological sign of Libra, varies from year to year.
For the rest of us, it’s one of two times a year when the Sun crosses the equator, and the day and night are of approximately equal length.
The upper panel shows that on an equinox , neither half of the Earth points directly towards the Sun.
At noontime in the Northern Hemisphere the sun appears high in the sky during summertime and low in the sky during winter.
The date when night and day are nearly of the same length and Sun crosses the celestial equator moving southward.
