Space Calendar: What to look for in the September skies

Not a whole lot happening in September, but a couple of events worth talking about.

Sept. 22

Autumnal (Fall) Equinox

The fall equinox arrives Tuesday, Sept. 22, at 8:05 p.m. EDT, the moment the Sun sits directly above the equator —shinning equally on both hemispheres.

That means most places on Earth will see almost exactly 12 hours of daylight and 12 hours of darkness — which is where the word “equinox” comes from, Latin for “equal night.” 

In central North Carolina, that means sunrise around 7:15 a.m. and sunset around 7:15 p.m. 

After this point, the Sun appears to cross the equator heading south, officially marking the start of astronomical autumn in the Northern Hemisphere.

Earth’s seasons come down to its tilt. The planet spins on an axis tipped about 23.5 degrees, and that angle stays fixed as it orbits the sun. For half the year, the Northern Hemisphere leans toward the sun, bringing longer days and more direct sunlight — spring and summer. For the other half, it leans away, spreading that same sunlight over a wider area for less warmth — fall and winter. 

The equinoxes mark the two moments each year when neither hemisphere is tilted toward or away from the sun, splitting daylight almost evenly worldwide.

Sept. 26

Full Harvest Moon

This year’s Full Harvest Moon arrives Saturday, Sept. 26, reaching peak illumination at 12:49 p.m. EDT. 

The Harvest Moon is the full moon that falls closest to the autumnal equinox, which occurred four days earlier on Sept. 22.

For several evenings, the moon rises soon after the sun sets, so early evenings stay bright well past dusk. Farmers once relied on that extra light to keep working the fields after sunset, gathering in summer-grown crops before the first frost — which is how the moon got its name.

The effect comes down to the angle of the moon’s orbit against the horizon this time of year. Most nights, the moon rises about 50 minutes later than it did the night before. But around the Harvest Moon, that delay shrinks to just 25-30 minutes, so the Moon seems to rise at nearly the same time several nights running — almost like a string of full moons in a row.

Look for it low on the horizon just after sunset, where it should take on the oversized, golden glow of the “Moon illusion.” Expect it to look essentially full for about three nights, from Friday through Sunday, so there’s room to spare if clouds move in on the peak night itself.

Neptune at Opposition

Neptune reaches its closest approach to Earth this evening, with its face fully illuminated by the sun.

The planet will shine brighter than at any other time of the year and remain visible all night, rising in the east around sunset and setting in the west at dawn. Because of its vast distance, Neptune appears only as a small blue dot even through large telescopes, and it’s too faint for the naked eye — binoculars or a telescope are required to spot it at all. For astrophotographers and dedicated skywatchers, it’s a challenging but rewarding target.

Moon phases: Last Quarter — Sept. 4, 3:52 a.m.; New Moon — Sept. 10, 11:27 p.m.; First Quarter — Sept. 18, 4:45 p.m.; Full Moon (Harvest Moon) — Sept 26, 12:49 p.m.