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The Sky This Week, 2011 May 31 - June 6

Short nights for long looks into deep space, Saturn courts a double star.
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Saturn, 2011 May 30, 02:05 UT
Imaged from Alexandria, VA, USA 


The Moon opens the month of June with a gradual return to visibility in the evening sky. She will cycle through her waxing crescent phases as she grows toward First Quarter, which occurs on the 8th at 10:11 pm Eastern Daylight Time. The New Moon that occurs on June 1st will have an unusual twist this year since it will produce a partial solar eclipse that’s best seen from the arctic regions. The only portion of the U.S. that will see it will be the northern half of Alaska, with the greatest coverage of about 20% of the Sun visible from Point Barrow. Across the pole, residents of extreme northern Norway, Sweden, Finland, and western Siberia will see about 60% of the Sun obscured as Old Sol skirts the horizon at local midnight! Look for Luna’s slender crescent very low in the west-northwest about half an hour after sunset on the 3rd. The following evening you’ll find her making an attractive triangle with Castor and Pollux, the Gemini Twins. On the night of the 7th she passes about seven degrees south of the star Regulus, heart of Leo, the Lion.

We’re now approaching the time of year when full astronomical twilight doesn’t end at dark-sky locations until nearly 10:30 pm. Morning twilight starts to send out its first tendrils before 4:00 am, which makes for a rather short time of astronomical darkness to enjoy the views of remote faint celestial objects. Unfortunately it’s also the time of year when we still have one of the most fertile hunting grounds for "faint fuzzies" well-placed for Northern Hemisphere stargazers. As winter’s bright stars set and before summer’s bright stars reach the meridian in the wee hours we’re looking away from the plane of our home Milky Way galaxy into the depths of intergalactic space. The region roughly bounded by the Big Dipper and the bright stars Arcturus, Spica, and Regulus is home to the heart of the great Virgo Galaxy Cluster, of which our Milky Way is a far-flung outlier. A modest 8-inch telescope can easily spy a hundred or more of the cluster’s brighter members, while larger scopes with more light-grasp can pick out several hundred more. There are several areas in this part of the sky where up to a dozen smudges of distant galaxies slowly waft through the wide-angle eyepiece on my 14-inch reflector at the same time. Although they are initially unimpressive, the trained eye will pick out differences in each one, and when you come to the realization that each one of those little fuzzballs is the combined light of hundreds of billions of stars they suddenly start to seem more impressive. If you can visit a dark site before the Moon returns later this week, take a telescope along and try to spot some of these distant cosmic neighbors.

If your wanderlust keeps you closer to home, you still have a ringside seat to study Saturn, which crosses the meridian in deep evening twilight. The golden-hued planet forms a large elongated triangle with the bright stars Arcturus and Spica when viewed with the naked eye, and he forms an even smaller triangle with a pair of stars when viewed through binoculars or a low-power telescope. The brighter of his two companions is the star Gamma Virginis, also known as Porrima. This is one of the most famous double stars in the sky and is one of the few that show marked changes in the separation and position angle of the component stars from year to year. I’ve been following Porrima through its recent "periastron" over the past decade. In 2000 the components were quite easy to resolve in my 8-inch telescope, but by 2004 when they passed closest to each other they revealed an elongated blob of light even with the Observatory’s 12-inch refractor. They have now opened up again to where they should be easily resolved in a four-inch telescope, and they have Saturn and his magnificent rings for a neighbor!

The morning twilight sky is still hosting three planets which you should be able to track down if you have a clear view to the east, clear skies, and a pair of binoculars. You shouldn’t need the glasses to spot Venus half an hour before sunrise. She’s only five degrees above the horizon, but her bright glow should be easy to find right up until the Sun comes up. You should also have no trouble finding Jupiter, whose cheery glow is some 10 degrees higher than that of Venus. In between is ruddy Mars, and here you’ll need your binoculars. Mars shines much less brightly than his companions, but he’s only about five degrees above and to the right of Venus so he should be fairly easy to track down. Look for his characteristic ruddy tint.

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