A Harvest Moon reaches peak illumination tonight: When to look up
As the nights grow long and the temperatures cool in the Northern Hemisphere, a new moon famed for its brightness and orange hue will rise in the sky.
The Harvest Moon, which has inspired no shortage of cultural touchstones – from a Nintendo game to Neil Young’s Billboard hit – occurs annually around the start of fall at a time when Earth's only natural satellite is especially close to our planet.
Because it rises near sunset and reaches peak fullness earlier, the Harvest Moon not only provides more working hours to farmers, but can provide quite a sight to skygazers across the hemisphere.
Here's what to know about this year's super Harvest Moon and how you can see the celestial body as it's also eclipsed by Earth's shadow.
Moongazing:Partial lunar eclipse to combine with supermoon for spectacular sight across U.S.
What is a Harvest Moon?
Unlike other moon names, the Harvest Moon is not associated with a specific month but, rather, occurs each year around the time of the autumnal equinox, according to the Old Farmer's Almanac. This means that the Harvest Moon can occur in either September or October, depending on how the lunar cycle lines up with the Gregorian calendar.
This year's autumnal equinox is Sunday, Sept. 22, but the Harvest Moon is rising in the night skies already.
When is the Harvest Moon?
The Harvest Moon appeared Monday and will last for three nights, ending in the early pre-dawn hours of Thursday morning, according to the Almanac.
The moon will reach peak illumination at 10:34 P.M. EDT Tuesday.
Why is it called a Harvest Moon?
During the nights preceding the autumnal equinox, the moonrise occurs sooner than is typical, resulting in an abundance of light earlier in the evening after sunset.
The extra light has traditionally provided farmers with more time to pick (or harvest) their crops, and so the name "Harvest Moon" was born.
Autumn is historically a busy time of year for farmers as they work past sundown harvesting the summer's crops, according to NASA. As such, moonlight became an essential part of farming.
According to NASA, the first known written use of the name "Harvest Moon" in the English language was in 1706, per the Oxford English Dictionary.
What does a Harvest Moon look like?
Many skygazers regard the Harvest Moon as appearing bigger, brighter and more orange than a typical moon.
But according to EarthSky, a website devoted to astronomy and Earth sciences, that may partly be due to an illusion. That's right: The way our brains process the view causes the moon to appear larger near the horizon than it does when it's higher up in the sky, NASA says.
Because most people look at the full Harvest Moon after sunset, when the celestial body has just risen, it naturally appears bigger as any full moon would, EarthSky says. It's proximity to the horizon – at least from a skygazer's vantage – is also what lends the moon an orange-ish hue as spectators must peer through a thicker portion of Earth's atmosphere than when gazing overhead.
The moon's orbit is not a perfect circle around Earth, which means that the full Harvest Moon's distance from Earth in any given year can effect how big it appears in our skies.
Harvest Moon coincides with lunar eclipse, supermoon
This year, the Harvest Moon is not only also a full supermoon, but also coincides with another celestial event: A partial lunar eclipse.
A supermoon occurs when a full moon coincides with the satellite's closest approach to Earth in its elliptical orbit. A lunar eclipse, meanwhile, results from the Earth moving between the sun and moon. This week, those three celestial bodies imperfectly align, creating a partial lunar eclipse as Earth’s shadow falls upon – but does not entirely cover – the surface of the moon.
This week's partial lunar eclipse should be visible Tuesday night across the entire northern hemisphere, including North America. For those in the United States, that means all lower 48 states should have a view.
According to NASA, the moon will enter Earth's partial shadow at 8:41 PM EDT, but it's the peak of the eclipse that viewers will want to witness. While the moon will slightly dim around 10:13 p.m., the peak itself will occur at 10:44 p.m.
Contributing: Doyle Rice, USA TODAY
Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]