Azernews.Az

Laman Ismayilova

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The seasons will turn in the early hours of September 23, when astronomical autumn arrives in Azerbaijan at exactly 04:05:08 Baku time.

According to the Astrophysics Department of the Faculty of Physics at Baku State University (BSU), this precise moment marks the autumnal equinox - the point in the year when day and night are nearly equal in length.

At the equinox, the Sun rises almost exactly in the east and sets almost exactly in the west. Yet the two sides of the day are not perfectly balanced: atmospheric refraction and the apparent size of the Sun's disk make daylight slightly longer than nighttime.

The equinox also marks an important point in the Sun's annual journey across the sky. The Sun crosses the celestial equator from the Northern Hemisphere into the Southern Hemisphere, bringing the start of astronomical autumn to the Northern Hemisphere and spring to the Southern Hemisphere. From then on, days in the north gradually grow shorter while nights become longer.

The changing seasons are not caused by Earth moving closer to or farther from the Sun. Instead, they result from Earth's yearly orbit around the Sun and the tilt of its rotational axis relative to the plane of its orbit. This tilt changes the angle at which sunlight reaches Earth's surface throughout the year, producing the familiar cycle of seasons.

Astronomical autumn in 2026 will last 89 days, 21 hours, 45 minutes and 1 second. The season will come to an end with the winter solstice on December 22, marking the beginning of astronomical winter in the Northern Hemisphere and astronomical summer in the Southern Hemisphere.