THIS week marked the official start of autumn – and we asked readers to send their best pictures.

From colourful auburn leaves to frosty dew-filled fields, we received some great images reflecting the start of the season.

Roughly around the same point each year, the autumnal equinox marks the point when the sun passes over the earth’s equator – creating a day and night that are the same length.

This year, the autumnal equinox fell on September 22.

The equinox – Latin for ‘equal night’ – occurs because of the earth is tilted on its axis, which is what creates the changing seasons.

During summer, the northern hemisphere is tilted towards the sun, creating longer days.

As the earth makes its way around the sun over the course of the year, the earth hits a point where neither the north nor south poles are tilted towards the sun.

Following the equinox on Thursday, the days will become shorter and the nights will become longer.

The autumnal equinox can occur on September 22, 23 or 24 each year.

There is sometimes confusion when autumn begins. This is because meteorologists – and therefore TV weather presenters – divide the year into four equal parts for statistical reasons. In this model, autumn is said to start on September 1.

The precise moment that the sun will passed the equator was at 3.21pm British Summer Time on Thursday, September 22.