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The Sky This Week, 2015 March 10 - 17

The other Milky Way...
NGC 2237/2244, the "Rosette" Nebula in Monoceros
Imaged 2015 FEB 14 from Morattico, Virginia

The Moon skulks along the southern reaches of the ecliptic this week, passing through the rising constellations of the summer sky.  Last Quarter occurs on the 13th at 1:48 pm Eastern Daylight Time.  She will greet you before sunrise as she wanes.  Look for Luna just over a degree north of the ringed planet Saturn among the stars of Scorpius before dawn on the 12th.   On the morning of 14th she is perched high above the “Teapot” asterism of Sagittarius.  The end of the week finds her slimming crescent gliding through the sparse starfields of Capricornus and Aquarius.

With the Moon ensconced in the pre-dawn sky we can once again turn our attention to winter’s bright constellations.  The March campaign for the citizen-science “Globe At Night” program begins on the evening of the 11th and runs through the 20th.  This world-wide observing program helps astronomers track the locations of sources of light pollution and helps you find dark sites to enjoy the splendor of the night sky.  This month our target of attention is the bright winter constellation Orion, which is well-situated near the meridian as evening twilight ends.  Compare your view of Orion on the next clear night with the star charts on the Globe At Night website and record your observations there.  This simple exercise will contribute to science and help define areas where the stars can actually be seen.

One of the overlooked features of the winter sky is the pale glimmer of the Milky Way, which bisects the bright stars of the Great Winter Circle.  Unlike the summer months, when we gaze toward the heart of our home galaxy, the winter months offer us a view in the opposite direction, toward the galaxy’s edge.  The star fields are much less dense in this part of the sky, but the nonetheless hold a number of celestial gems for your perusal.  Just to the left of Orion is the dim constellation Monoceros, the Unicorn, a “modern” constellation dating to the mid-16th Century.  Although there are over 60 stars associated with this group, none of them are brighter than fourth magnitude, but the real gems are the abundant star clusters and gaseous nebulae that can be seen with binoculars or a small telescope.  One of the best of these objects is NGC 2244, the “Rosette” Nebula.  This tenuous cloud of glowing gas surrounds a compact cluster of bright stars and is one of the most photographed objects in the “deep sky”.  Sweeping your binoculars down into the stars of Canis Major will reveal more of these wonderful stellar knots sprinkled among the brighter stars of this more prominent constellation.

The early evening sky finds Venus pulling away from the much dimmer planet Mars as evening twilight falls.  The dazzling planet is making steady progress against the encroaching Sun and can now be seen well after the onset of astronomical darkness.  Venus will continue to move eastward against the background stars, eventually overtaking Jupiter toward the end of June.

Jupiter continues to be the night’s dominant planet, well-placed for viewing throughout the evening hours.  Old Jove continues to slowly drift westward against the stars of the dim spring constellation of Cancer, the Crab.  You’ll have an interesting opportunity to see some of the giant planet’s most interesting phenomena on the night of the 14th.  The smallest Galilean moon Europa will drag its shadow across the planet’s disc that evening with the moon itself emerging from the disc at around 10:00 pm.  Half an hour earlier the moon Callisto will begin to transit the planet’s face.  Since Callisto’s surface is very dark compared to the bright clouds of Jupiter’s atmosphere it will resemble a shadow as it makes its way across.  Throughout the evening the planet’s Great Red Spot will also be visible, so hope for clear skies!

Saturn reaches the first stationary point in this year’s apparition on the 14th.  For the next few months the ringed planet will creep westward among the stars in the “head” of Scorpius.  The best views of Saturn still occur before sunrise.  Thanks to Daylight Time this now occurs at a more reasonable time for many of us, but that’s about the only benefit I see from the time change.


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