See the Spring Triangle and Saturn tonight

The Spring Triangle stretches across the eastern sky around 10 p.m. last night. It's formed by the star Arcturus (upper left), Saturn (top right) and Spica (below Saturn). Photo: Bob King

I’m not the first to call it the ‘Spring Triangle’ but the name sure fits. We’re talking about Arcturus, Saturn and Spica and what a fine figure they cut in the eastern sky from 10 o’clock onward. I suppose it was inevitable given our fondness for triangles of bright stars that one should pop up in spring. You’re probably already familiar with the Summer Triangle and the Winter version, so why not one for spring?

Unlike the Summer and Winter standbys, this one’s only good for a year. That’s because one its members, Saturn, like the other planets, never stays put in one place. Next year the planet will have slid eastward and lie to the left of Spica. No triangle there. However, in 2013 it will be positioned below Spica and form a new, wider triangle with its starry pals.

The current triangle is huge, bright and really catches the eye. You can squeeze three fists held at arm’s length between Saturn and Arcturus. Spica and the planet are just a fist apart. Start your spring with this fun, connect-the-dots exercise tonight.

Cassini spacecraft chronicles the change of seasons as it captures clouds concentrated near the equator of Saturn's largest moon, Titan. This picture consists of an average of three images taken using a filter sensitive to near-infrared light, which 'see' through Titan's haze to its surface and lower atmosphere, plus an image in visible light. Credit: NASA/JPL/SSI

Speaking of Saturn and spring, we’ve already seen rain a few times here in Duluth, a welcome sign that the season is underway despite stubborn single-digit nighttime temperatures. Saturn’s largest moon Titan also experiences seasons, with changes in cloud cover depending on the season. Back in 2004, during late southern summer, the Cassini spacecraft photographed extensive clouds in Titan’s south polar regions.

The photo above was taken in October 2010, about a year into Titan’s southern fall, and shows a few clouds in the south, but most are now concentrated in a bright belt around the moon’s equator. The clouds may look familiar, but they’re composed of methane, the principle ingredient in the natural gas we use to heat our homes back here on Earth. Because Titan and Saturn are nearly a billion miles from the sun, it’s much colder there, allowing methane to exist as ice, liquid and cloud.

A huge arrow-shaped storm, measuring 930 by 750 miles, blows across the equatorial region of Titan last September. This storm darkened large areas of the moon, likely from methane rain. Credit: NASA/JPL/SSI

Scientists believe that methane evaporating from lakes on Titan’s surface rises to form clouds, which then release methane ‘rain’ during rainstorms, refilling lakes and creating new ones.

“It’s amazing to be watching such familiar activity as rainstorms and seasonal changes in weather patterns on a distant, icy satellite,” said Elizabeth Turtle, a Cassini imaging team associate at the Johns Hopkins University Applied Physics Lab in Laurel, Md.

Spring has been underway since 2009 in Titan’s northern hemisphere. Storm clouds in the photos above have swept over the moon’s equatorial regions and left what appear to be dark, methane rain-soaked ground and replenished lakes in their wake.

Clouds move above the large methane lakes and seas near the north pole of Saturn's moon Titan. The outlines and color of the lakes have been enhanced for clarity. Credit:Â NASA/JPL/SSI

Those lakes are even colder than those in my part of the world. Temperatures on the surface of the moon hover at -290 F. Titan has hundreds of lakes brimming with methane and ethane. Largest is the 150,000 square mile Kraken Sea, nearly five times bigger than Lake Superior! The moon may be an alien world, but it’s the first place beyond Earth where we’ve seen stable bodies of surface liquid.

Saturn and Titan tonight. The view shows directions reversed with south at top and east to the right, the way you'd see it in most telescopes. Created with Stellarium

You can see this wintry world for yourself in even a small telescope. Tonight Titan is at greatest elongation (maximum distance) east of Saturn. 25x and up will show it as a small ‘star’ four ring lengths due east of the planet. If you’re using an 8-inch or larger scope, you’ll even be able to see Titan’s orange color.

Those willing to invest a little more time can watch Titan move closer to Saturn over the coming nights. The moon completes an orbit around the ringed planet in 16 days.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

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