Hexagons on Saturn, Spots on Mercury

You’ll find plenty to look at in the May shallow sky.

The jewel is Saturn, well up by nightfall and remaining visible through most of the evening. Since it’s at quadrature (the point when a planet is exactly 90 degrees from the sun as viewed from Earth), the shadow of the planet on its rings will be especially prominent. That makes this month an excellent time to show Saturn to your friends and relatives. But then, when isn’t a good time to show Saturn to anyone?

Alas, you probably won’t be able to see the Weird and Wonderful hexagonal storm around Saturn’s north pole, shown in the Cassini pictures from last month. The storm has actually been there for quite a few years: it was first seen by Voyager I in 1980. But it’s tough to see from here. You really need a polar view to show the hexagonal structure of the storm.

But if you want a Saturn – related challenge that you can try from home, Iapetus’ dark side is pointed toward us on May 24. Did you get a chance to look for it last month, when it was shining at magnitude 10.1 with its bright side facing our way? Now’s your chance to see Iapetus’ other side as it fades to a dim magnitude 11.9. Get a finder chart and more information about Iapetus from Jane Houston Jones’ page at http://www.otastro.org/iapetus/

Meanwhile, Jupiter is rising a bit before 10 p.m. as it heads toward an opposition in early June. Start observing it now, get back in practice seeing its bands and moons and moon shadows, and you’ll be ready to observe the subtle details of the bands by opposition when the viewing really gets good. Unfortunately Jupiter is quite far south this year, and only climbs to about 30 degrees by the time it transits. We’ll have to get used to a low Jupiter, though; it won’t get much better this year.

Venus continues its amazing run in the evening sky. Its phase is just barely gibbous.

Mercury is invisible early in the month, but by May’s end it emerges into the early evening sky. It crosses perihelion (closest approach to the sun) on the 9th. Did you catch the news item last month about the new image of the unknown side of Mercury? Until now, the best images of Mercury come from Mariner 10 1974, which captured images of less than half the planet’s surface. The rest of Mercury remained essentially unphotographed ... until now. Gerald Cecil of UNC – Chapel Hill used a remotely – operated telescope in Chile to shoot Mercury when it was very close to the sun, using a cloth mask to block out stray light. Cecil’s photo (which I haven’t been able to find online) is apparently quite fuzzy, mostly bright and dark spots which presumably correlate to craters on Mercury’s surface. Just goes to show how little we know about our own solar system!

Mars, Uranus and Neptune don’t rise until the wee hours of the morning, and you’re best off waiting a few months unless you find yourself up just before dawn itching to look at a planet. Pluto rises earlier, just after dark, and transits a few hours after midnight. It’ll get a little brighter in a few months, but if you just can’t wait, it’s certainly a viable target in May.

Finally, there’s a comet in the sky. And not just any comet, but one discovered by an SJAA member, Don Machholz, from Loma Prieta way back in 1986. 96P/Machholz, Don’s third comet, will become visible in the morning sky starting in mid April, at about 9th magnitude, and continues to be visible through the first half of May. As May opens, the comet rises a bit after 2 a.m. and will be passing a bit south of lambda Pegasi, heading gradually west. Stay up late and catch a glimpse!