SJAA Ephemeris January 2013 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Stormy Weather

Akkana Peck


“There’s so much to see on this side of Jupiter that it’ll keep you busy all night.”



Jupiter is high in the sky all night this month – and its storms offer lots of wonderful detail to see, if you’re lucky enough to get steady skies and avoid the storms down here on Earth.

The Great Red Spot (GRS) seems unusually complex this year. Some observers, or at least imagers, are seeing detail inside the spot. There’s a dark central core, and a small white oval farther out near the edge of the spot, on the side nearest Jupiter’s equator. Some of this should be visible visually with good optics and sufficiently steady skies. Even if you can’t see the interior detail, there’s the spot itself, and a wealth of turbulence in the South Equatorial Band (SEB) following in the wake of the GRS.

Leading the GRS, and a little farther south, is “Oval BA”, also known as “Red Junior”. First seen in 2000 when several white ovals collided, it’s now a small but fairly dark red spot.

And there’s a new spot – an even darker, smaller spot – between GRS Jr. and the GRS proper.

South of the GRS, toward the south polar region, look for a series of small but prominent white ovals in the South Temporal Band (STB).

There’s so much to see on this side of Jupiter that it’ll keep you busy all night.

When the GRS isn’t pointed toward us, there’s still plenty to look at. Jupiter’s North Equatorial Band (NEB) sports two elongated white ovals along the north side of the band. They’ve been drawing closer to each other over the last few months, and there’s some chance they might merge into one larger oval. You might also have a chance to catch a dark feature in another part of the NEB that’s shaped like a tadpole – Christopher Go caught it on CCD last month.

The South Equatorial Zone has some white ovals of its own, three of them, much smaller than their northern cousins. Plus there are lots of swirls and monster festoons in the equatorial zone, rifts in the NEB, and other assorted detail all over the planet.

And of course, there are the moons. Most of this month’s double transits (two moons, and/or their shadows transiting at the same time) take place during the day, where they’re a lot less spectacular to watch and more difficult to observe. But Jan 24 offers a twilight and early evening pass of Ganymede, Io, and Io’s shadow. The initial Io transit starts in broad daylight, around 2:30 pm, and by sunset, Io’s shadow is just exiting Jupiter’s disk. If you set up just after sunset, around 5 or 5:30 pm, you can catch Io’s shadow and Ganymede in transit.

It’s a good thing there’s so much to see on Jupiter, because none of the other planets are particularly well placed this month. Uranus and Neptune are high enough to catch in the evening – try as soon as it gets dark, since they only get lower from there. Mars rises at about 10 and doesn’t transit until the wee hours of the morning. Saturn, too, is best viewed as a morning object, rising several hours after Mars, and Mercury is just barely visible in the early morning dawn early in January. Pluto is too close to the sun all month.

And if it’s too cloudy to see Jupiter, you can always go to the web for the latest planetary spacecraft news. Last month was fun. NASA had a leak leading everybody to expect historic news from the Mars Curiosity rover – “one for the record books” – then had to backpedal and say well, it found some organic compounds – “organic” being defined as “containing carbon and hydrogen”. Chlorinated methane, to be specific. Not exactly the big evidence-of-life news implied by the initial rumors – and it’s possible that the compounds are contamination from Curiosity itself, so further study is required.

But wait – what should hit the news only a few days later? NASA’s Messenger spacecraft, in orbit around Mercury, found definitive evidence of water ice in some of the shadowed craters at *Mercury’s* north pole. Not only that, but it also found evidence of organic compounds.

Bet that’s not where you’d look first, for either water or organics.

But Mercury has very little axial tilt, so it doesn’t have seasons the way the Earth does. And that means that the interior of a crater at one of Mercury’s poles can stay in shadow indefinitely, never seeing sunlight. So water ice (or anything else) can potentially remain in there for a long time.

Of course, no one is suggesting evidence of past life on Mercury.

The organic compounds were likely deposited there by impacts from comets and meteorites. (All the news reports I’ve seen say “comets and meteorites.” Is a piece of a comet making impact on a planet not considered a meteorite?) Still, I love the irony. Organic compounds on Mercury! While we were all so busy looking at Mars!

Ain’t science grand?


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