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The Sky This Week, 2010 July 6 - 13

An exotic eclipse, Jupiter joins the evening planets.
ThunderMoon_04_WP_small.jpg
Moon and Thunderhead, 2010 June 22
Imaged at the U.S. Naval Observatory with a
Canon PowerShot S2IS digital camera,
1/100s @ f/5.6, ISO 50

The Moon is a thin waning crescent in the pre-dawn sky for most of the week.  New Moon occurs on the 11th at 3:40 pm Eastern Daylight Time.  At this time Luna crosses the ecliptic plane directly in front of the Sun along a path stretching across the South Pacific Ocean from several hundred miles southeast of Tonga to the rugged southern coast of Chile and the southernmost reaches of Argentina.  Most of the eclipse path lies over vast stretches of ocean, but it comes tantalizingly close to Raratonga in the Cook Islands and makes its first landfall on Mangaia in the same island chain.  The Moon’s shadow continues eastward, where it passes just south of Tahiti, then travels on past the Tuamotu Islands before scoring a near bull’s-eye on Rapa Nui, also known as Easter Island.  This is one of the most remote eclipses in recent memory, but many people will be watching from cruise ships dispatched from Raratonga and Tahiti.  Several hundred more will view it from amongst the silent Moai statues on Rapa Nui in what can only be one of the most unusual experiences one can find on the planet.  If you miss this one (and most of us who aren’t already en route probably will) the next total solar eclipse will occur on 2010 November 13.  Unfortunately this one also occurs mostly over the South Pacific as well!

Those of us left behind can take advantage of the Moon’s absence and hope for another spell of mild weather to enjoy the delights of the midsummer night sky.  I was fortunate enough to spend the holiday weekend out on Virginia’s Northern Neck, far from any major city lights, and the view of the rising summer Milky Way and the colorful stars embedded within was a very refreshing sight.  High in the east as twilight fades is a triangle made up of the bright stars Vega, Deneb, and Altair, each of which has a bluish-white tinge.  As you turn to face south you’ll see the ruddy star Antares scudding above the southern horizon, surrounded by the distinctive outline of Scorpius, the Scorpion.  To the east of the scorpion is the teapot-shaped asterism of Sagittarius, the Archer, above which lie the densest star clouds of the Galaxy.  Sweep the area from the Summer Triangle down to the “spout” of the teapot with binoculars or a small, low-power telescope and you will be richly rewarded with countless stars, star clusters, and gaseous nebulae.

If you’re unable to beat the heat and escape the city and suburbs, the evening sky still puts on a good show as twilight fades to darkness.  The western sky plays host to three planets in a sort of cosmic horse race that will play out over the next few weeks.  The participants are Venus, Mars, and Saturn, and each night this week the three objects become mutually closer together.  Venus does most of the hard charging, moving about a degree per night eastward toward Mars and Saturn.  On the evening of the 9th she passes just one degree north of the bright star Regulus, which Mars passes just a month ago.  She will then set her sights on Mars himself, but the red planet will scoot south of Saturn before she catches up to him.  Saturn, in the meantime, will watch these two worlds overtake and pass him by the end of the month.  

By the end of the week Jupiter officially enters the evening sky, rising just before midnight in the Washington area.  The giant planet more or less lords over this part of the sky, only receiving monthly visits from the Moon.  Otherwise, no bright objects will steal his thunder in the star-poor autumnal constellations for the rest of the year.  Jupiter is a welcome sight for owners of small telescopes.  His generously-sized and ever-changing disc is a welcome sight to those of us who have been staring at the smaller and nearly featureless surfaces of Venus, Mars, and Saturn.

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