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The Sky This Week, 2013 November 5 - 12

Bright Moon in the west, bright stars in the east.
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Lunar craters Theophilus & Cyrillus
Imaged 2013 SEP 24, 10:08 UT


The Moon returns to the evening skies this week, wending her way through the dim autumnal constellations as she waxes to First Quarter phase, which occurs on the 10th at 12:57 am Eastern Standard Time. Look for Luna’s crescent above the dazzling disc of Venus in the southwestern sky at dusk on the 6th. For the rest of the week she’s pretty much on her own. With little competition from other bright attractions this will be another good week to get to know the Moon’s many interesting attractions. Virtually any optical aid will transform her from a silver-flecked light in the sky to a place with stark, sun-drenched landforms. On the evening of the 8th point your telescope at the Moon to see one of my favorite lunar landmarks, the prominent "double crater" pair of Theophilus and Cyrillus. They will be very prominent, about halfway between the cusps along the terminator line. Theophilus is the fresher of the two craters, with much of its ejecta blanket filling the floor of Cyrillus. Theophilus is about 100 kilometers (61 miles) in diameter and 3.3 kilometers (11,000 feet) deep. Its prominent central peak rises nearly 1.5 kilometers (one mile) above its floor. As impressive as this crater may appear, looks can be deceiving. If you were able to stand on the floor of the crater about halfway between the terraced walls and central peak, you would think you were on a vast, flat plain. Since the Moon is a much smaller sphere than the Earth, your apparent horizon is much closer, on the order of 1.5 kilometers (one mile), and the curvature of the surface drops away very quickly.

Now that we’re back on Standard Time, you won’t have to wait too long to see bright stars return to take the place of the faint autumnal constellations. By 10:00 pm the colorful stars of the Great Winter Circle are filling the eastern sky, led by the familiar figure of Orion, the Hunter. This constellation straddles the celestial equator and is visible from just about all the inhabited parts of the globe. It is therefore no surprise that Orion can be found in the sky lore of just about every civilization that has existed since the beginning of recorded history. It is one of the few constellations mentioned by name in The Bible, and it is even a fixture in the skies of J.R.R. Tolkien’s "Middle Earth". Orion and I have shared many nights together under crisp viewing conditions, and the light from his prominent stars has long served to help brighten up long winter observing sessions.

Venus gets a visit from the crescent Moon early in the week as she passes through the teapot-shaped asterism formed by the brightest stars of the constellation Sagittarius, the Archer. If you have binoculars and a clear southwest horizon you can watch her as she passes under the teapot’s "top". She now sets almost an hour after the end of evening twilight, so you can briefly catch her in all her glory against a dark-sky background.

You won’t have to wait too long for the setting Venus to be replaced by another bright planet. Giant Jupiter now rises in the east-northeast at around 9:00 pm, adding even more dazzle to the bright stars of the Winter Circle. By 11:00 pm he’s high enough to corral in the telescope, and the view only gets better as the night progresses. Old Jove has been putting on a splendid show so far this year with lots of activity in his prominent equatorial cloud belts and a resurgence of the Great Red Spot, which is finally beginning to live up to its name. On the night of the 8th you should have an excellent view of the Red Spot at around 11:00 pm that will last well past midnight. As an added bonus, Jupiter’s largest moon Ganymede will be transiting the disc in the Red Spot’s wake. Watching the dynamics of the planet and its moons at such special times will probably get you hooked on observing this vast, far-flung world.

Mars rises at around 1:30 am, so your best views of the him will still be just before dawn. You’ll find him slowly drifting eastward below the belly of Leo, the Lion high in the east as morning twilight gathers. He’s not much to look at right now, but if you have a very steady morning airmass you should be able to see his bright north polar icecap on the edge of his pink disc. Mars is clearly in the sights of planetary scientists this month. India launched its first Mars probe on the morning of the 5th, and NASA will dispatch its own probe to the red planet on the 18th.

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