Jupiter at Opposition October 29, 2011

Jupiter Photo by NASA

Known as Zeus by the ancient Greeks, and the fifth and largest planet in our solar system, will be at opposition to the Earth on the 29th of this month. "Wait...Oppo..what?!"... Well O.K., let me explain.

Unlike Earth, it takes Jupiter 12 long years to orbit the sun verses the one year for Earth, so each year we zoom past it and wave as we orbit the sun. The point where Jupiter is directly opposite in the the sky from the sun is called "Opposition". Basically, if you looked at our solar system from the top down, the Sun, Earth, Jupiter would be in a straight line with Earth in the middle. At this point, Jupiter can be seen in the sky all night until dawn, and we'll be at this point of opposition in 10 more days.

Why is this year so special? Don't we reach opposition with Jupiter on each and every pass? Well, yes we do, but this year is a little different. You see the planets orbits aren't exactly circular, they're all slightly elliptical and at times they're closer to the sun then at other times. The point when a planet is closest to the sun in it's orbit is called "Perihelion". This year Jupiter was at perihelion with the sun back in May bringing it 75 million km. closer to the sun this year then it was while at it's farthest distance from the sun. This is called "Aphelion". Earth was at aphelion with the Sun in June, a month later during the summer solstice. So basically, both planets are close enough to each other for us to get a nice gander at our Jovian neighbor. And what a sight it is.

Jupiter is usually the fourth brightest object in the nights sky after the Sun, Moon, and Venus, but occasionally has to give up that honor whenever Mars comes poking around. This summer, Jupiter has the limelight all to itself as both Venus and Mars are too close to the Sun to be very spectacular. Jupiter varies in visual magnitude from -1.6 at it's dimmest at "Conjunction" with the sun ( I know, more strange words) to about -2.9 when It's at opposition on the 29th of this month. If you haven't noticed it in the nights sky this past summer you should probably put the remote down and go outside more because it is a spectacular sight. It's been so bright in fact you can sometimes see it shining through a completely overcast sky. That's pretty crazy, huh?

I'm usually pretty good at knowing when these things are coming, but this one seemed to slip past my radar until it was shining me right in the face back in June. In fact, one could have seen Jupiter in near peak magnitude back in September of last year when the Earth was reaching it's farthest point in space from the sun and Jupiter within 5 months of it's closest point to the sun. No matter, it was better to wait until it was at opposition so we don't have the pesky sun getting in the way.

With the naked eye, Jupiter looks just like a really bright star in the sky, but even with the cheapest pair of binoculars such as a tasco 10x50mm you should be able to see a few of Jupiter's largest moons: Ganymede, Europe, Io, and Callisto. With this setup you'll see an image similar to what you see below. You won't see any detail in Jupiter itself like the NASA image above, but the prize here is seeing the moons of Jupiter. I mean, come on. We've all seen other planets in night sky before, but how many of you have seen other moons besides our own? If I was prepared for this event (and I wasn't) I would have taken the year leading up to it to buy myself a nice telescope such as the Orion EON 120mm f/7.5 ED Apochromatic Refractor Telescope. Even a really cheap one would allow me to see some coloring and slight detail in the planet. The next time we'll have another opportunity to see Jupiter this bright in the nights sky will be in the fall of 2022. Don't let that stop you. Jupiter is available to see almost year round, and with a half way decent telescope, it won't matter that it isn't the closest it can be. But for those of you like myself that don't have the money to run out and buy a nice telescope, this is the best time to grab your cheap binoculars and take a look and see the moons of Jupiter without a telescope.

Jupiter with Moons Taken with my Sony DSLR with Zoom lens

Originally Published on 10-19-2011 09:21 AM