September equinox: Equal day and night as the Sun crosses equator today

The equinox is an annual event that happens twice a year, in March and September, when the Sun's rays fall directly on the equator.

In Short

• The day and night durations become roughly equal everywhere on Earth
• It is a temporary pause in the gradual shortening or lengthening of days
• In India, the September equinox heralds the arrival of autumn

Parts of the world including India will witness equal hours of day and night on Sunday as the Sun crosses the equator marking the September equinox.

On September 22, 2024, at precisely 6:13 PM IST, the September equinox will occur, marking a pivotal astronomical event.

This moment signals the Sun's crossing of the celestial equator from the northern to the Southern Hemisphere, resulting in nearly equal hours of day and night across most parts of the globe, including India.

What is September Equinox?

The equinox is an annual event that happens twice a year, in March and September, when the sun's rays fall directly on the equator.

As a result, the day and night durations become roughly equal everywhere on Earth. This balance of daylight is a temporary pause in the gradual shortening or lengthening of days, depending on the hemisphere.

What happens in Northern Hemisphere?

In India, the September equinox heralds the arrival of autumn.

As the Sun moves southward, the Northern Hemisphere enters the cooler months, with days growing shorter and nights longer.

This event is also known as the autumnal or fall equinox, a shift that traditionally signals the end of the monsoon season and the start of cooler, crisper days.

What happens in Southern Hemisphere?

The Southern Hemisphere experiences the opposite effect, with the September equinox marking the beginning of spring. As days grow longer and nights shorter, the region welcomes warmer weather and increased sunlight.

Despite the common perception of the equinox as the day when day and night are perfectly equal, this balance isn't entirely accurate due to atmospheric refraction and the Sun’s apparent size.

The equinox is defined by the exact moment the Sun crosses the equator.

After today, the Sun will continue its southward journey, eventually reaching the Tropic of Capricorn during the December solstice.

The September equinox points to Earth's constant motion and the changing rhythms of nature, as we transition from one season to the next.