The Opposition of Jupiter and the Moon

Hey, hey, everyone. Thanks for stopping by!

If you’ve had a bit of luck with your night skies, just a little, you may have noticed a bright light in the east by mid-evening lately. The planet Jupiter’s back! Jupiter’s always great to see, and I find the sight of it, even with the naked eye, to be particularly inspiring. I find most naked eye things to be, you’re right, but Jupiter’s one of my favorites. I like to imagine the moons, and the rings, and the storms, and the stripes. If you’re fortunate to have even a small telescope or a big pair of binoculars, you can even see the four big moons; the Galilean ones. As far as I’m concerned, any night with Jupiter in the sky is better than any night without. It’s a lot like baseball, I guess.

If you’re looking for an excuse to get out and see it, the late part of this week’s and into the early part of next is the time to do it. This coming Friday, April 7, is a big day for us and the king of planets. Jupiter will be at opposition!

As everything zips around the sun, sooner or later, a couple those things cluster together in a straight line. Opposition is the moment when three things, the sun, a vantage point (for example, Earth), and a third thing (Jupiter) are in a straight Sun -> Earth -> Jupiter line. Seen from our viewpoint here, Jupiter is opposite the sun in the sky. So, as the sun sets, Jupiter rises. See the connection there? Opposition is the time when an object is opposite the sun in the sky.

The days right around opposition are a great time for observing because it’s the time when objects tend to be at their biggest, brightest, and most fully lit. If you’re the sort of person who likes to stand around shining flashlights on soccer balls, you can see what I mean. When you shine the light straight on the ball, it’s big, bright, and the whole face of it is lit. If you move the ball part off to the side, it’s not fully lit anymore, because some of the light misses, goes off into space, and lights up your second grade class photo hanging on the wall.

We can extrapolate this into a conversation about how the moon’s phases work, and maybe that’d be good for another day. This might sound familiar, though. Can you picture it? Remember, when Jupiter’s at opposition, it’s a 400 million mile-long Sun-Earth-Jupiter line, and the flashlight in the middle of the solar system is shining straight on Jupiter, lighting its whole face.

Does this ring a bell? Right! It’s the same arrangement the moon is in when it’s full, but, instead, it’s 239,000 miles of a Sun-Earth-Moon line. When the moon is full, it’s directly opposite the sun in our sky, is completely lit, rises at sunset… see? Since we have a name for it, the full Moon, saying “the moon’s at opposition” is scientific, and maybe a little pedantic, but not wrong. I guess you could also say “Jupiter’s full,” but… you probably wouldn’t.

Things at Opposition
Things at Opposition

Did someone mention the full Moon, though? Well get a load of this. This coming Monday, April 10 and into the 11th in the US (the moon is exactly full at about 6AM UTC) , is the night of the Full Oink Moon, so named for all the… pigs… no… wait… that’s the Full Pink Moon… so named for all of the wild flowers blooming everywhere. Where I am, nothing’s blooming but mud, but the Full Brown Moon is somewhat less appealing isn’t it?

On the night of the 10th, the bright, just-a-couple-days-past-opposition Jupiter, the full Moon, and Spica, the brightest star in Virgo, and night’s 16th brightest, will rise into the night and put on a spectacular show until sunrise washes them away. The Moon and Joops will be only a couple of degrees apart in the sky, just the width of a finger or a finger and a half (I don’t want to know where you’re getting your half fingers) held out at arm’s length. This’ll be a good night to grab some passers-by, point at the sky, and say “See!!” Once you’ve used the moon to help find Jupiter, it’ll be easier to find night after night for the rest of the year, as Jupiter and Spica travel the skies together.

The Moon, Jupiter, and Spica, April 10, 2017
The Moon, Jupiter, and Spica, April 10, 2017

It’s all just an optical illusion, though, a trick of perspective. Jupiter’s 40 times bigger than the moon, but it’s also over 1700 times farther, so there’s no real contest here.

Incidentally, if you were standing on Jupiter, looking in toward the sun at the moment of opposition, you’d see the nighttime side of Earth. This is the same arrangement as when there’s a new moon.

There you have it. An opposition two-fer. I hope you can see it, and see Jupiter at its best for 2017. Clear skies, everyone!


8 thoughts on “The Opposition of Jupiter and the Moon

      1. Yeah. I like it because it changes more quickly than Saturn does. It moves more than Saturn does. The moons, like yous say, move. It’s just great. I remember the first time I saw Jupiter through a telescope. The big bright light with these tiny little dots next to it. I don’t think I realized what I was looking at until hours later. The next time I saw them was through my big binoculars. It’s always surprising. All this said, I wouldn’t be upset if I could get another shot at Saturn some time soon. 🙂

        Liked by 1 person

    1. Hi, Sabra, yeah, the exact moment on fullitude (?), so, the moment when the moon and sun are exactly 180 degrees apart in Earth’s sky (one on one side, the other on the other) is at about 6:00 AM UTC on Tuesday the 11th, like you say. That’s about 2AM US Eastern, 11 PM Monday US Pacific, and 8pm in Hawaii. I figured I’d stick with th US perspective on the timing mostly because I think most of the people who stop by here are in the US, but also because it’ll be daytime or just before moonrise for most of the world at 6 AM UTC Tuesday. What this means is it’s true the full moon is on the 11th, but in the places where it’ll be able to be seen when it’s full, it’ll still be the 1oth. Either way, it’ll look full both nights; tonight, the 10th, and tomorrow the 11th. You make a good point, though. I’ll clarify this post and make it clearer from here out. Maybe I’ll even use this idea for its own post later on, maybe for May’s full moon. Thanks for the tip, and for reading.

      Liked by 1 person

      1. Thanks so much for the detailed clarification! I just wanted to double check for my own records and make sure I wasn’t telling people the wrong info during my shows!

        Liked by 1 person

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