Temporary Moons

Jupiter has at least 63 moons orbiting it, and thousands of asteroids and other rocks littering its orbital path (not considered moons because they don't revolve around Jupiter). Between 1949 and 1961 it had another one, when Jupiter grabbed a comet and turned it into a moon. The comet goes by the romantic name of "147P/Kushida-Muramatsu" and it hung around for 12 years, roughly two orbits, before traveling back out into the black.

Like so much in the world of orbital mechanics, the closer you look at this, the weirder it gets. The comet is a "quasi-Hilda comet," meaning it's from the Hilda family of asteroids. These asteroids - there are thousands of them - form a triangle within Jupiter's orbit, around the 2 main Lagrange points (where the gravity between Jupiter and the sun cancel each other out), and the point opposite Jupiter. You don't see alotta triangles in space. Circles, spirals, ellipses are the usual suspects.



Apparently, according to the wiki article, the triangle "breathes," meaning the density of the wall of the triangle relative to the points is constantly shifting (at least, that what I think it means; I've read the sentence about ten times and am still not sure).

As I've said a hundred times in these posts, random movements form non-random structures, many of them quite complex. The idea that they are formed due to a few simple laws - namely Kepler's three laws of planetary motion - is to me infinitely more interesting, and more beautiful, than the idea they were put in motion by some kind of intelligent design.

I pulled the illustration of the Hilda triangle from the wikipedia article.

Moonshadow

I read about this yesterday, and dreamed about it last night. Vividly. So I'm gonna try to go out and see it, if only to see dream imagery appear in real life.

Trippy.

Two moons of Jupiter (Europa and Ganymede) are going to be simultaneously casting shadows on Jupiter Thursday and Friday. A pretty rare event. Jupiter clears the horizon about 8 p.m. or thereabouts, so go out and take a look. Admittedly, you need a telescope to see this one, and I think Gordo is the only one out there with access to one, but go out and look anyway. It's such a pretty planet. It'll be the brightest thing in the eastern sky. Take your wife, your husband, your kids, your neighbor, your girlfriend. Point it out to them. Impress them with how much you know. Maybe you'll get lucky.

Here's video of one moon shadow (Ganymede's) on Jupiter, taken with an amateur camera and telescope, no less. Imagine how cool two will look.



Thanks to the One Minute Astronomer for the heads up, and the video.