The head of the Jordanian Astronomical Society, Ammar Al-Sakji, said the autumn equinox will occur early Wednesday, marking the astronomical start of autumn in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere. Astronomical autumn will last approximately 90 days.
اضافة اعلان
This year’s autumn equinox will occur at 3:05 a.m. Jordan time on Wednesday, when the Sun, in its apparent annual motion, crosses the celestial equator from north to south.
On the day of the equinox, the Sun will rise from a point very close to due east and set from a point very close to due west.
Although it is commonly said that day and night are exactly equal in length on the day of the equinox, this is not entirely accurate from an observational perspective, as daylight lasts slightly longer than 12 hours.
This is mainly due to atmospheric refraction, which causes the Sun to appear above the horizon while its actual geometric position is slightly below it. It is also due to sunrise and sunset times being calculated based on the upper edge of the Sun’s disk rather than its center.
In Amman and its surrounding areas, the length of daylight comes closer to 12 hours several days after the equinox.
On September 26, daylight will last approximately 12 hours and one minute, while on September 27 it will be approximately 11 hours and 59 minutes. Therefore, the closest observational equality between the lengths of day and night will occur roughly between these two dates.
The changing seasons are not caused by variations in the distance between Earth and the Sun, but by the tilt of Earth’s rotational axis by approximately 23.4 degrees relative to the perpendicular to its orbital plane around the Sun.
This tilt, combined with Earth’s orbit around the Sun, causes changes in the angle at which sunlight reaches Earth and in the length of day and night throughout the year.
One indication of this is that Earth is actually closer to the Sun during winter in the Northern Hemisphere, in early January, and farther from the Sun during summer, in early July.
Following the autumn equinox, the Sun will gradually rise from positions south of due east and set from positions south of due west as viewed from Jordan.
Its altitude in the sky at noon will also decrease, while daylight hours will gradually shorten and nighttime hours increase.
This apparent movement will continue until the winter solstice in December, when the Sun reaches its southernmost declination and the Northern Hemisphere experiences its shortest day and longest night of the year.
Astronomical autumn in 2026 will extend from the moment of the autumn equinox early Wednesday, September 23, at 3:05 a.m. Jordan time, until the winter solstice on December 21 at 11:50 p.m. It will last approximately 89 days, 20 hours and 45 minutes, or nearly 90 days.
The lengths of the astronomical seasons vary slightly from year to year due to the elliptical nature of Earth’s orbit around the Sun and changes in its orbital speed.
Earth moves at different speeds along its orbit in accordance with Kepler’s second law.
The autumn equinox provides an astronomical opportunity to observe the relationship between Earth’s movement and the daily changes visible in the sky.
Over several days, observers can track changes in the positions of sunrise and sunset and the gradual shortening of daylight, offering an annual illustration of the effects of Earth’s orbit around the Sun and the tilt of its rotational axis.
The Jordanian Astronomical Society will document these phenomena through astronomical observations.
