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The Sky This Week, 2014 September 30 - October 7

All eyes on the Moon!
The Moon, 2014 March 11, 03:10 UT
The terminator line runs from the southern highlands (left) through the Oceanus Procellarum
and the large circular Mare Imbrium.  The prominent crater near upper center is Copernicus.

The Moon brightens the evening sky this week, waxing to her Full phase which occurs on the 8th at 6:51 am Eastern Daylight Time.  October’s Full Moon is popularly known as the Hunter’s Moon.  The geometry that produced the Harvest Moon last month is similar this time around, only that instead of providing extra light for farmers to bring in the harvest there’s now a little extra light for hunters to chase game across the stubble of the reaped fields.  Luna starts the week among the bright stars of Sagittarius, then drifts through the barren starfields of the autumn constellations.


This is another good week to study our nearest neighbor in space.  The terminator line advances nightly as Luna waxes through her gibbous phases revealing some of the Moon’s most interesting terrain.  In particular, the day/night line advances over the largest of the so-called lunar “seas”, the Oceanus Procellarum, or “Ocean of Storms”.  This large smooth plain is dominated by ancient lava flows that erupted from the nearby Mare Imbrium, the “Sea of Rains”, the largest circular feature on the Moon’s face.  This gigantic feature is the result of an impact by a large asteroid early in the history of the solar system some 3.8 billion years ago.  It is noted for its relatively smooth surface that bears the occasional pock-mark of smaller impacts as well as numerous “wrinkle ridges” formed as adjacent lava pools cooled and hardened.  Compare these vast stretches with the jumbled. Shoulder-to-shoulder craters of the Moon’s more ancient southern highlands and you’ll get some idea of the incredible violence that shaped the primordial solar system.  You don’t need a large telescope to enjoy these sights.  Even a steadily-held pair of binoculars will show these large-scale features quite nicely.


As a bonus, in the wee hours of the morning of the 8th, the Moon undergoes a total eclipse, passing through the northern half of the earth’s shadow.  This particular eclipse favors residents of Hawai’i and the west coast, but we’ll see a substantial part of it here in the east before Luna sets at 7:16 am EDT.  If you’re up early that morning, the penumbral phase begins at 4:15 am.  Half an hour or so later you may notice a subtle shading encroaching on Luna’s left edge which will gradually become deeper until 5:15, when the Moon encounters the edge of the umbral shadow.  Luna should be fully immersed in the shadow by 6:25 am, and mid-eclipse will follow at 6:54.  You may have a hard time finding the Moon after that unless you’re farther west near the Rocky Mountains, where you’ll see the end of totality at 5:24 am Mountain Daylight Time and the end of the umbral phase at 6:34 MDT.  If you miss this one don’t fret; there will be two total lunar eclipses visible from the US in 2015!


The bright planets are now confined to the early evening and pre-dawn skies.  You can still catch a quick glimpse of Saturn low in the southwest during evening twilight, but any telescopic inspection of the planet and his magnificent rings is now tempered by the turbulence caused by his low altitude.  He sets shortly after the end of evening twilight.  Ruddy mars is now racing through the stars of Scorpius, and this week he puts considerable distance between himself and his ruddy rival, the bright star Antares.  He will continue to pace the ever-encroaching Sun, but he’ll hold his own against the day-star and will remain visible through the end of the year.


Bright Jupiter is now best seen before dawn, well-placed high in the east an hour before sunrise.  Jupiter is slowly drifting eastward among the faint stars of the constellation of cancer, the Crab, and he’ll brighten this otherwise drab stretch of the sky throughout the coming winter and spring.  Give him a look if you’re up getting the morning paper.




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