SJAA Ephemeris July 2011 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Saturn and Spirit

Akkana Peck


Saturn is still the best target in July evening skies, its rings tilted about eight degrees.

Catch it in the southwestern evening sky after sunset.

It’s getting a bit low to see detail, about 50 degrees up as night falls, but you’ll still be able to see the major ring divisions described in last month’s column – and more.

Take a look at the body of the planet: there’s detail to be seen in Saturn’s cloud bands. If the night is at all steady, you should be able to see some of the cloud bands on the planet’s northern hemisphere, the one tilted toward us, with most small telescopes.

What colors do you see? Saturn’s bands are much more subtle than Jupiter’s, but look for contrasts in pastel shades of yellows, browns and greens.

If the seeing is good, crank up the magnification and try for further detail. There’s a storm going on in the North Polar Region that’s well within reach of good amateur scopes. You don’t need huge aperture, just good optics and steady air. You may also be able to discern some storm activity in the North Equatorial Band, if you look carefully.

If you haven’t tried sketching a planet, this is a great time to try it. Saturn is fairly easy to sketch, and you’ll be amazed how well sketching trains your eye to see subtle details like those storms. With Saturn, it helps to start with a template, so you can concentrate on the interesting details of the rings and bands rather than fussing over trying to get the exact shape of the rings right. But I found it surprisingly difficult to locate Saturn templates online, so I’ve made one you can use for the next few months.

Had enough of Saturn? Mercury is visible after sunset, with greatest separation from the sun on the 20th.

Neptune rises a bit after 10pm, with Uranus an hour and a half behind it. They should be good late-night targets if you’re staying up late at a star party, or morning targets if you rise before dawn.

July 12 marks a Neptune-related milestone: the completion of one Neptunian orbit (165 Earth years) since the planet was discovered on September 23, 1846. Except it’s not quite as simple as that: factors like the precession of Earth’s axes (which changes the coordinate system we use to specify planetary positions) affect how we measure Neptune’s orbit. If you bought a copy of the 2011 RASC Observer’s Handbook from the club this year, check out the interesting article on page 9 for the details. They conclude that July 12 is the date Neptune completes one sidereal year since its discovery – a measurement that relies on coordinates relative to radio sources outside our own galaxy, and not anything to do with the motion of the Earth. Happy first anniversary, Neptune!

Pluto transits at midnight, though it’s low in the sky, only 33 degrees up, so you’ll want clear skies to chase down this distant 14th-magnitude speck. It’s still in the heart of the Sagittarius Milky Way, roughly halfway between the nebula M24 and the open cluster M25

– so it’s a rewarding area for sweeping, but a very difficult place to identify one 14th-magnitude pinpoint among all the others. The chart in this year’s RASC Observer’s Handbook is less help than usual, since it doesn’t identify the stars on the chart; it’s indexed to Uranometria, so try matching the RASC chart to the Uranometria page. Otherwise, you might do better with a planetarium program. Either way, you’re in for a tough fight ... good luck!

You can catch Venus in the dawn sky early in the month before it vanishes in the sun’s glow. Jupiter and Mars, too, are in the morning sky.

And let’s all raise our glasses to the Mars Spirit rover. NASA officially gave up trying to reach Spirit at the end of May. It’s been more than a year since Spirit’s last radio transmission; the dust storms and frigid Martian winter, combined with solar panels at the wrong angle to catch the sun, must have depleted the rover’s batteries.

The rover team did an amazing job. Spirit and Opportunity were originally designed for a three-month mission, covering about a kilometer each. That was back in January of 2004! Spirit lasted over 6 years and

7.7 kilometers (4.8 miles). She beamed over 124,000 images back to Earth, along with copious other data pointing to Mars’s wetter past.

She climbed hills steeper than anyone originally planned for, and overcame flash memory problems, dusty solar panels and a stuck wheel. While dragging that wheel, she uncovered bright white soil that turned out to be a concentrated silica deposit, pointing to past hot springs or steam vents.

Meanwhile, Spirit’s sister rover, Opportunity, is still going strong. At just past 30 km (over 18 miles), Opportunity is enroute to Endeavour crater, taking spectra of rocks along the way.

Together, those two rovers have amassed quite a list of accomplishments ... not bad for what was planned as a 3-month, 1 km mission!


Previous | Contents | Next