Observe the Moon…. Week…?

Hey, Sky Fans!

This Saturday, October 16, 2021, is International Observe the Moon night!

Since 2010, NASA has been encouraging people to take a night to look up and observe the Moon, and do it together. There are events going on. So maybe you can head out and find one near you. You can find more information about events and other cool stuff at NASA’s Observe the Moon Night page.

But why wait?

Instead, let’s grab a late cup of coffee, start tonight and keep an eye on the Moon from tonight through the weekend and see where things take us.

In the western dusk as the Sun sets, we’ll see the planet Venus, bright and beautiful.

Then, farther toward the south as the skies darken, we’ll see the Moon nestled between two giant planets. Saturn to its left, and Jupiter to its right. Take a minute here to look, not just at the Moon, but at the two planets and notice how they look relative to each other. Jupiter’s the third brightest thing in the night sky after the Moon and Venus, and it really shows. I mean, seriously, it’s absolutely stunning these days.

It’s always amazing to me to think about what we’re seeing that when we look at it.

What we’re seeing is reflected sunlight from a ball of gas and other stuff, big enough to hold a thousand Earths, a half billion miles away. That light comes from the Sun (as sunlight typically does), which is so big that it can hold a thousand Jupiters. Still, even though the light has traveled all that way from the Sun to Joops and then took about 30 light minutes to bounce all the way back to your eye, it’s still unmistakably bright.

Compare that to Saturn. It’s only about 20% smaller than Jupiter but it’s more than twice as far away from us. It’s so far that the Saturn we see is actually the Saturn of 80 minutes ago. Next to Jupiter, it looks frustratingly muted and dim. “Really? That’s it?” Someone once said to me.

Let’s try to imagine the Moon and those two planets in three dimensions. The Moon right near by, only a quarter million miles away, and then the two planets pushing our line of sight deeper and deeper into the night.

Each night the Moon moves about 13 degrees eastward from our point of view. That’s a little bit more than the width of your first if you hold it out at arm’s length. That’s our view of the distance the Moon travels in its orbit over 24 hours. Every night, night after night, 13 degrees. So, now we can predict where the Moon will be tomorrow night. Just hold your fist out tonight, stare off into space, and mark off where you think it’ll be.

By the same time tomorrow (Friday, the 15th), the Moon will be a bigger waxing gibbous and will have jumped to the other side of Jupiter. Is it where you predicted?

It's Observe the Moon night this weekend, but let's get a head start and take a look starting tonight!
The Moon, Saturn, Jupiter, and Neptune — October 14 – October 16, 2021

Come Saturday the 16th, it’ll be even more gibbousey (it’s a word now!) and in an open patch of sky without a lot else going on. Out in that direction, too dim for us to see without a telescope, is the planet Neptune. It’s in the cold and dark 30 times farther from the Sun than we are. Incidentally, the Moon’s phase Saturday night is about the same as it was the night Pete Conrad landed Apollo 12 in the Ocean of Storms (El Océano de Tormentas!) in November 1969.

There, stretched across that sky, is the long line from Venus to Neptune and then on to Uranus, which is farther toward the east, and will take a couple days for the Moon to catch up with. Mars and Mercury are too close to the Sun at the moment for us to do anything with.

That line is called the ecliptic, and represents the path the Sun takes across the sky. Since all the major planets and most of the minor planets orbit around the Sun’s midsection, that line also represents our view of the plane of the solar system. So visualizing that line lets us looking out across the very floor of the solar system, and see where all our neighbors are.

It’s a great time to look at the Moon and use it to track down other excitement in the skies. Have a great weekend, and a great Observe the Moon Night, everyone. Thanks for stopping by, and clear skies!

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