Stargazing for September 2020

Full Corn Moon and the Autumnal Equinox

August 31, 2020
Moon and Girl

Ready to see some shooting stars? Here are a couple fun astronomical tidbits to enjoy this month.

Catch the Corn Moon

September’s full Moon, which is traditionally called the Corn Moon, will appear on the night of Tuesday, September 1! Look southeast after sunset to watch it rise above the horizon. Read more about the Corn Moon here.

Not a Harvest Moon This Year!

Sometimes, September’s full Moon takes on the name “Harvest Moon” instead of “Corn Moon.” The full Moon that happens nearest to the date of autumnal equinox (September 22 or 23) always takes on the name “Harvest Moon” instead of a traditional name—a rule that often places the Harvest Moon in the month of September. However, when September’s full Moon occurs early in the month, the full Moon of early October lands nearest to the autumnal equinox and takes on the Harvest Moon title instead. That’s what happens this year!

The Autumnal Equinox

In 2020, the autumnal equinox—also called the September equinox or fall equinox—arrives on Tuesday, September 22!

The autumnal equinox marks the astronomical start of the fall season in the Northern Hemisphere and of the spring season in the Southern Hemisphere of Earth.

What Is an Equinox?

The word “equinox” comes from Latin aequus, meaning “equal,” and nox, “night.” On the equinox, day and night are roughly equal in length.

During the equinox, the Sun crosses what we call the “celestial equator”—an imaginary extension of Earth’s equator line into space. The equinox occurs precisely when the Sun’s center passes through this line. When the Sun crosses the equator from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox (the spring equinox).

After the autumnal equinox, the Sun begins to rise later and nightfall comes sooner. This ends with the December solstice, when days start to grow longer and nights shorter.