As the calendar turns to September, the leaves on trees across the northern tier of the United States start to turn a tinge of yellow, orange and brown, a taste of what’s to come this fall in forests across the country. However, for stargazers September marks the return of longer nights with a slate of astronomical events unfolding in the early autumn sky.
Not only will nights become longer than days across the Northern Hemisphere in September, but the weather will also help to bring the night sky into focus. The gradual downturn in humidity results in crisper views of the night sky, a stark difference from the muggy summer nights that can make some stars look slightly fuzzy.
The Autumnal Equinox that’s due this year on September 23, is traditionally the official start of astronomical autumn across the Northern Hemisphere and astronomical spring across the Southern Hemisphere. This date varies from year to year due to the Earth’s imperfect orbit around the sun. At that point, the sun’s most direct rays will be pointed at the equator, resulting in around 12 hours of daylight and 12 hours of nighttime everywhere around the globe.
However, due to the inconsistencies in the start and end dates of astronomical seasons, meteorologists follow the calendar rather than the orbit of the Earth around the sun to determine the seasons. Meteorological autumn officially begins on September 1 and concludes on November 30 every year. This method is not only more consistent, but it makes it easier for forecasters to compare seasonal statistics from one year to another.
Still, considering the debilitating heat wave that has been baking most of the globe all Summer, the Autumnal Equinox is feeling a little more like the advent of the Fall Season for many.
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