Harvest Moon meets Uranus this weekend

Harvest Moon (photo by Steve Wilson)

“The Night Sky” has been running continuously in these newspapers for almost four decades. During that time, the Harvest Moon has been the subject every few years. You’d think that everything about it has already been said. But this year brings a surprise – a twist.

First, though, a reminder that the Harvest Moon this Saturday night looks no different from any other Full Moon. It’s not bigger, redder, lower, higher or anything else. Yet it isn’t merely a meaningless label for the September Full Moon. Hmm, not just a name, and yet it doesn’t look special. What’s left?

Behavior, that’s what. The Harvest Moon acts differently from other Full Moons. The Moon normally comes up about an hour later each night. But the Harvest Moon rises just 20 or 25 minutes later on successive evenings. Result? From Thursday (September 27) right through Monday (October 1), we’ll see a series of full or nearly-full Moons rising at dusk again and again.

Tying this into the traditional myth is easy. Farmers trying to finish harvesting work by nightfall are given a helping hand with the light of the Full Moon conveniently appearing at sunset. (Of course, alternatively, they could simply turn on their tractor lights.) That this goes on for several nights in a row is the only thing that makes the Harvest Moon a special Full Moon.

By contrast, the early spring Full Moon also rises at sunset, but then the next night it doesn’t come up until 90 minutes later, and another 90 minutes the following night. So in spring we get just a single evening of full moonlight, and then the Moon goes AWOL. A few nights later and it doesn’t make an appearance until midnight. It’s here and then it’s gone.

Don’t bother using a telescope. The Harvest Moon is a dud. The even illumination on its surface washes out all craters and mountain ranges. And its bright light spoils the rest of the sky, too, so the Milky Way will be absent. The five classical planets can withstand such a brightness onslaught, but this is one of those odd months when not a single bright planet is out until nearly midnight. So there’s almost nothing worth watching telescopically.

Almost, but not quite: Turns out that the seventh planet, Uranus, reaches its closest to Earth of 2012 that very same night. It too will be exactly opposite the Sun in the sky, which is where the Full Moon lurks. Result: They’re next to each other.

On Saturday night, just below the Harvest Moon floats green Uranus. It should show up through binoculars (thanks to its emerald color) as a little star a short distance below the Moon. If you’re with people, be sure to say “YOUR-in-us,” and don’t pronounce it the other way. It deserves some respect because Uranus was the “God of the Heavens” in both Roman and Greek mythology. It’s the only planet that’s not solely a Roman deity. It alone has no Greek analogue. For example, the Greek analogue of Mars is Ares, Jupiter Zeus, Venus Aphrodite and so on. So Uranus is unique. And so is the most famous Full Moon of the year: a Saturday night twofer.



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