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The Sky This Week, 2010 June 1 - 8

Getting together: Mars meets Regulus, Moon meets Jupiter
Saturn & Titan, 2010 May 26, 02:55 UT
Imaged from Alexandria, VA, USA with a 20-cm
(8-inch) Schmidt-Cassegrain Telescope

The Moon slips into the morning sky this week, gradually waning as she passes through autumn’s rising dim constellations.  Last Quarter occurs on the 4th at 6:13 pm Eastern Standard Time.  Luna doesn’t have much company in this rather barren stretch of the sky.  However, on the mornings of the 5th and 6th she shares the same patch of sky with bright Jupiter as twilight begins to brighten the short nights.

The Moon’s departure for the morning hours means that stargazers can once again spend some time out in dark skies hunting down the more elusive “faint fuzzies” of the “deep sky”.  Unfortunately we’re approaching the time of the year’s shortest nights, and there are many interesting targets to command one’s telescopic attention.  In the hour after the end of evening twilight there’s still time to track down some of the hundreds of external galaxies that haunt the region bounded by the stars of the Big Dipper, Leo, the Lion, and the bright star Spica in the constellation Virgo.  Dozens can be glimpsed in a six-inch instrument, while my 14.5-inch Dobsonian will show a dozen in one field of view if pointed at the right place!  These faint swatches of light are literally distant cousins of our Milky Way galaxy.  As far-flung members of the Virgo Galaxy Cluster they are gravitationally bound to the same giant elliptical core galaxies that control the motions of the Milky Way and other members of the Local Group.  By the early morning hours the summer constellations are beginning to dominate the sky along with the flowing shimmer of the Milky Way itself.  The “deep sky” objects that lurk here are all much closer to home, being made up for the most part of clusters of stars and glowing clouds of luminous gas within the Galaxy’s nearby spiral arms.  This part of the sky is a treat for small telescopes and binoculars, and will be best placed for viewing in another month or so.

Brilliant Venus may be found in the western evening twilight sky, an unmistakable beacon as darkness descends.  By 10:00 pm you should be able to make out the Twin Stars of Gemini, Castor and Pollux.  Venus slides toward the duo during the course of the week, forming nightly triangles of varying acuteness until the week’s end, when she lines up with the stars.  She sets about 40 minutes after the end of astronomical twilight, and gradually begins to lose ground to the Sun as the month progresses.

Mars spends the week in a rendezvous with the bright star Regulus in the constellation Leo.  The red planet starts the week some three degrees from the star, and on the evening of the 6th he passes less than a degree to the north of the Lion’s heart.  Once past Regulus he’ll set his sights on Saturn, passing the ringed planet by the end of July.

Saturn gradually resumes direct eastward motion against the stars this week, but most of us would be hard-pressed to notice.  He’s been located within the same telescopic field as a 7th magnitude background star for the past several weeks, and he’ll stay near this star for another couple of weeks to come.  His rings have passed through their minimum tilt as seen from Earth this year, and over the rest of his apparition they will gradually begin to open up, exposing their northern face to our scrutiny.

Jupiter continues to puzzle early morning skywatchers with the nearly complete disappearance of one of his prominent equatorial cloud belts.  This feature is usually one of the easiest to see in a small telescope, visible in just about anything that can resolve the planet’s disc.  However, right now it is essentially absent, visible as a very subtle shading in large telescopes.  The belt has a history of pulling similar fading acts, and when it decides to return it usually does so with quite a surge of activity.  Stay tuned!

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