Look Up Tonight! It's the Super Hunter's Moon
Sorry to say it, but your view of the Moon won't be as good as it was for ESA astronaut Tim Peake on March 28, 2016, when he captured this image of the Moon setting from the International Space Station. Image credit: ESA/NASA
Look up at the sky tonight, October 16, and you'll be treated not only to a full moon, but a supermoon. And not just any supermoon, but a Super Hunter's Moon!
WHY A FULL MOON IS FULL
Let's go over the fundamentals first. If nothing else, take away from this article the knowledge that the Moon's phases have nothing to do with the Earth's shadow. Yes, it kind of makes sense: the dark crescents, the predictability, and the orbits: one around the Earth, and both around the Sun. Shadows crossing orbs. But when the Earth's shadow crosses the Moon, you get a lunar eclipse.
The Moon's phases are a lot simpler than that. First, the Moon orbits the Earth every 29.5 days. You might have noticed that "moon" and "month" are similar words. That's not by accident. Moreover, the Moon is "tidally locked" with the Earth, which means from down here, we only see one side of the Moon, ever. Keep this in mind.
One half of the Moon is always fully illuminated by the Sun. As it creeps around the Earth over the course of a month, the illuminated area changes. When the Moon is generally opposite the Sun relative to the Earth (i.e. Sun-Earth-Moon), the side we can see is in full sunlight. It's a full moon. When the Moon is between the Sun and the Earth (Sun-Moon-Earth), the far side of the Moon—the half of it we never see—is in full illumination. In other words, the half we do see is receiving no sunlight at all. This is a new moon. (N.b. that there is no "dark side of the Moon." Every side of the Moon gets bathed in sunlight over the course of a revolution.)
The rest of the Moon's phases proceed from these fully lit or totally darkened states of visibility. As the Moon's orbit around the Earth takes it away from the Sun, it is said to be waxing, because from our point of view, the Moon is becoming increasingly full. After crossing the halfway point (the full moon), the visible Moon seems to darken. It is waning.
WHAT'S IN A NAME
Not all full moons are created equal. Sometimes the full moon seems really, really big. Sometimes it seems weirdly small. This is because the Moon's orbit around the Earth is not a perfect circle, but rather, is elliptical. Sometimes it is closer to the Earth than other times. When it is close, it is said to be at perigee. When it is farthest away, it is at apogee. When the Moon is both at perigee and full, you get what is colloquially called a supermoon.
So what about this Hunter's Moon business? That is what some Native Americans called the full moon in October for reasons that must seem obvious. It provided extra light by which to hunt—a vital activity with winter's fast approach. (You might recall last month's harvest moon, whose name has the same rationale as this one: Gather your acorns before snow blankets the forest.)
HOW TO SEE IT
Look up. Other things you'll see: tiny flickering dots that are stars, unless they're moving quickly, because those are likely airplanes or the International Space Station. If they're moving really, really fast, they're meteors. If you see a tiny stationary dot that doesn't flicker, it's probably a planet (or the tip of a cell phone tower). The super hunter's moon will make planet spotting more difficult. Uranus is at opposition this weekend and thus fully illuminated by the Sun from our point of view, but unless you're a first-rate astronomer with heavy duty hardware at your disposal, you won't be able to see it. The full moon above and light pollution below will join forces to wash it out. Even under the best conditions, it's really difficult to find. If you just vaguely point in the direction of the Moon and say, "See that dot? That's planet Uranus," people will probably believe you, though.
One more thing: Because we get a full moon this weekend, Halloween night will have a new moon. In other words, the night sky is going to be really dark: perfect conditions to test out your new clown costume and the response time of the local police department.