In what has been marked as a special occasion for centuries, a harvest moon appeared above the horizon Wednesday night.
A harvest moon is the full moon that is closest to the fall equinox, which marks the first day of autumn on most calendars and is when the earth is not tilted toward or away from the sun, which means people will get approximately 12 hours of daylight and 12 hours of darkness, said Judy Vondruska, an astronomy and physics instructor at South Dakota State University.
The term harvest moon came from a time when agriculture was the primary focus in America. A full moon in early fall provided farmers enough light to continue harvesting much later into the night than they could on most evenings, Vondruska said.
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A harvest moon's color isn't actually different than any other time the moon rises or sets, she said.
The reddish orange color often seen when a moon rises or sets is the result of scattering of the reflected sunlight from the moon passing through more atmosphere when near the horizon. Red and orange light are affected least by this scattering and so the moon can take on these colors in the process of rising and setting.
A harvest moon also is not necessarily any larger than any other full moon, she said. Although the moon has an elliptical orbit and sometimes is closer to the earth, which makes it appear larger, that will not be the case for this year's harvest moon, Vondruska said.
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