Tonight, from 8:30-9:30pm, Bicycle Astronomy will be down in front of the Red Dove, showing people the Moon and Jupiter. This happens to coincide with the opening for the latest edition of Geneva13, a zine of the local. Come on down and grab a copy and a Hot Toddy at the Dove, step outside and check out Jupiter and the Moon.
Why are they dancing? Well, Jupiter just happens to be just about at opposition. This means it’s opposite from the sun from our point of view. Another way of saying it: the earth is currently in between the sun and Jupiter in more or less a straight line. The significance of this? Nothing really. Set a bunch of planets spinning around a star and oppositions will happen all the time. It doesn’t mean you should cash in your IRA tomorrow and bet the Trifecta.
The moon is also at opposition. This happens every 28 days or so, and when the moon is opposite the sun, we get a full moon. (Or a lunar eclipse, if the moon happens to pass into earth’s shadow. That actually happened a little bit earlier this morning…a penumbral eclipse. But that’s another story.
So the moon and Jupiter are hanging out together. Here’s the view east from my driveway. Jupiter is upper left from the moon. Go out and check it out…over the course of the evening the pair will be getting higher in the sky. If you have binoculars, point them at Jupiter. And look through them. Maybe that was obvious. Anyway, you should see three or four of Jupiter’s principal moons. Ganymede is currently traversing Jupiter’s surface and you’re not likely to see it with binoculars. In order from left to right, the moons you will see in binoculars as little stars are: Europa, Io, Ganymede (if you can see it) and Callisto. Each one of these satellites is a unique world unto itself. Jupiter is almost like a little solar system. Europa is covered with an ice sheet that may obscure a huge liquid ocean with giant jellyfish in it. Io is a volcanic mess, with lava and sulphur. Ganymede is equal parts water and ice, and might also have a subsurface ocean. Callisto has a lot of ice, too, though it’s more like our moon…geologically inactive and pockmarked with craters.
Here’s the scene outside my driveway a little while ago:
Interesting fact: The three inner moons of Jupiter are in a 1:2:4 resonance. For every one orbit of Ganymede, Europa orbits twice and Io orbits four times. That doesn’t mean you should finally tell your boss how you feel about him, nor that it’s time to finally defrost the mystery package at the back of your freezer. The facts of the universe can be beautiful without directly having anything at all to with us. Unless of course we’re looking at them and appreciating the beauty. Which you can do, tonight!