September Equinox: Sun to Cross Equator This Weekend
By Graham Jones. Published 19-Sep-2024
At 12:43 UTC on September 22, the Sun will lie directly above the equator—giving every city in the world roughly equal hours of day and night.
At the September equinox 2024, the Sun will cross from the Northern to the Southern Hemisphere at a point close to Liberia’s capital Monrovia, on Africa’s western coast.
©iStockphoto.com/mtcurado
“Equinox” = “Equal Night”
In the Northern Hemisphere, the September equinox is the autumnal or fall equinox—it is when night starts to become longer than day.
Meanwhile in the Southern Hemisphere, it’s the spring equinox, and day starts to become longer than night.
One thing both hemispheres have in common is that on the day of equinox, every town and city has roughly equal amounts of day and night.
Equal day and night can also happen in June!
The Sun and the Equator
However, the astronomical definition of equinox is not based on daylengths.
For astronomers, the equinox is the moment the Sun crosses the celestial equator. This is another way of saying that the Sun lies directly above a point on Earth’s equator.
At the September equinox, the Sun passes from north to south of the equator. It continues southward for the next three months or so, reaching its southernmost latitude (the Tropic of Capricorn) at the December solstice.
The Crossing Point
The Sun symbol on our Day and Night World Map shows the subsolar point—the location on the globe where the Sun is directly overhead. This is the map at the moment of the 2024 September equinox.
©timeanddate.com
This year, the Sun will cross the equator from north to south at 12:43 UTC on Sunday, September 22. The above image from our Day and Night World Map shows the subsolar point at this moment.
Where exactly will the Sun pass over the equator? It will be at a point in the Atlantic Ocean with latitude 0.0° (the equator) and longitude 12.4° west. This is around 720 km (450 miles) south of Monrovia—the capital city of Liberia in West Africa.