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The Sky This Week, 2014 March 11 - 18

What to look for in a bright Moonlit sky...

The Moon, 2014 March 11, 03:09 - 03:12 UT

Imaged with the U.S. Naval Observatory's 12-inch (30.5-cm) f/15 Clark/Saegmüller refractor.
Composite image made with a Canon EOS Rebel T2i DSLR.

The Moon brightens the overnight hours this week, waxing to her Full phase on the 16th at 1:08 pm Eastern Daylight Time. The Full Moon of March is variously known as the Worm Moon, Crow Moon, Sap Moon, or Lenten Moon. Since it occurs near the point in the sky that marks the autumnal equinox, it is one of the few Full Moons in the year that is visible from the entire surface of the Earth. Luna spends the week gliding eastward from the stars of the Great Winter Circle toward the rising stars of spring. Look for the Moon near the bright star Regulus in Leo, the Lion on the evenings of the 13th and 14th. Late night skywatchers can watch her rise in the company of ruddy Mars and the blue star Spica at around 9:30 pm on the night of the 18th.

The first few nights of the week are good ones for exploring the surface of our natural satellite. Some of the most interesting lunar formations reveal themselves in the nights before Full Moon as the terminator line slowly sweeps across the vast lava plain known as the Oceanus Procellarum, or "Ocean of Storms". Lunar nomenclature harkens back to the earliest telescopic observations of her battered face, when primitive telescopes could just distinguish between the bright battered "highlands" and the smoother, darker "seas". We now know that the Moon is a lifeless, airless sphere that has been battered by countless planetessimals, asteroids, and meteoroids over the eons, but these details took many years to figure out after Galileo had his first tantalizing glimpses over four centuries ago. Optics have come a long way since that time, and even the smallest of telescopes will show features that eluded the great astronomers of the 17th Century. In particular look for "ghost" craters in the Mare basins that have been nearly swallowed up in the prodigious lava flows and the "wrinkle ridges" of solidified lava frozen like permanent waves on the basin floors. Subtle "albedo" features also abound on these vast plains, many of which have no corresponding topographic counterparts. These features become particularly prominent at Full Moon, when all of the topography is washed out by the direct rays of the Sun.

Jupiter still dominates the evening sky, beaming down with his regal glow from his high perch among the stars of Gemini. Jupiter resumed direct motion eastward against the stars on March 6th, so he’s gradually re-tracing his steps through the constellation’s rich Milky Way starfields. The giant planet is now well past opposition, so there is an appreciable angle between Old Jove, the Earth, and the Sun. You can see this for yourself on the evening of the 13th, when you’ll find the moon Europa emerging from a transit across the planet’s disk during evening twilight. Once the sky darkens you’ll see Europa’s shadow trailing far behind the moon, gradually working its way across the cloud tops before slipping off the planet just after 10:00 pm.

Ruddy Mars rises just before 10:00 pm as the week opens, and each succeeding night he comes up five minutes earlier. He is now very easy to find in the southeastern sky, far outshining the nearby bright blue star Spica. On the evening of the 18th the planet and star will be joined by a bright waning gibbous Moon which should provide an interesting photo opportunity. The planet itself is now entering the prime observing season for owners of modest telescopes. Summer is approaching in Mars’ northern hemisphere, so the north polar ice cap is rapidly shrinking. Some of the water vapor liberated by this seasonal thaw condenses around the high volcanic peaks of the Tharsis region and can be seen quite well with a six-inch telescope under steady conditions.

Saturn inches his way back into the evening sky, rising just before midnight by the end of the week. The ringed planet’s golden tint should be easy to spot low in the southeast during the early morning hours, but your best view of him will still probably be before dawn. Thanks to daylight time this isn’t as excruciatingly early as it was a week ago, but the rapidly climbing Sum will soon be brightening the sky earlier than most of us would like!

Venus is also best seen before sunrise. Although she is very low in the southeastern sky as twilight gathers she is very hard to miss. She is currently about as bright as she can get, so she should be visible right up to the time Old Sol breaks the horizon.

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