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The Sky This Week, 2010 May 18 - 25

Looking over the overlooked Moon, and Jupiter loses a stripe!
The Moon, 2009 November 22, 23:45 UT
Imaged from Shoestring Observatory
with a 50-mm f/10 "Galileoscope" refractor
and a Canon PowerShot A95 digital camera

The Moon waxes in the evening sky this week, passing a number of bright stars and planets as she goes.  First Quarter occurs on the 20th at 7:43 pm Eastern Standard Time.  Look for Luna to the southwest of ruddy Mars on the evening of the 19th.  On the 20th she cozies up to within 5ive degrees of the bright star Regulus in Leo, the Lion.  On the 22nd she gives golden Saturn a wide eight-degree berth to the south of the planet, and finally, on the 24th, passes five degrees south of the bright star Spica.

Luna’s waxing presence in the sky pretty well wipes out good views of the “deep sky” from dark locations, but the Moon herself is probably one of the most fascinating objects you can see in the “near sky”.  Amateur astronomers often say that our only natural satellite is “looked over, then overlooked” by owners of new telescopes.  While the desolate lunar surface has remained essentially unchanged since it was first documented by Galileo over 400 years ago, it is still the only world beyond out own where we can see exquisite detail with very modest optical aid.  This is a perfect week to get to know Luna’s pock-marked landscapes.  With each successive night a new set of features is revealed along the “terminator”, the line demarcating sunrise and sunset.  A majority of these features were named by astronomers who were the successors to Galileo and bear prosaic names like “Sea of Tranquility”, “Ocean of Storms”, or “Bay of Rainbows”.  A few evenings spent with some basic lunar maps will have you rattling off the names of features to your friends and neighbors as if you lived there.  I often tell passers-by when I have my telescope trained on the Moon that I know my way around Luna’s surface better than I know my way around Maryland!

Complementing the view of the Moon this week is an evening sky offering several planets.  The easiest one to spot is the dazzling white glow of Venus, which stands out in the west during the deepening hours of evening twilight.  This is not a particularly good evening apparition for this lovely object since she sets just over 40 minutes after the end of twilight.  This is about as far as she will stray from the Sun this year.  Under ideal circumstances she can set almost four hours after the Sun, high enough to cast shadows at dark-sky locations.  This year she’ll spend most of the next several months well-placed in waning twilight before slipping into the morning sky by mid-autumn.

Mars lingers in the sky until well after midnight as he closes the gap between himself and the bright star Regulus.  The red planet ends the week just six degrees west of the star, and he’ll close this final gap by June 6th, when he drifts just north of the star.  There’s not much to look at here anymore unless you have a large telescope under very steady skies.  His disc is just over six arcseconds across, and most of us see little more that a small pink-hued gibbous dot.

Saturn gets a visit from the Moon on the evening of the 22nd, and it’s an easy hop with the telescope from the relative proximity of Luna to the distant cold depths of the solar system near Saturn.  Light from the ringed planet now takes 75 minutes to reach us from his distant perch, but a generously sized disc and sharp, pointed rings are easy to see in almost any telescope, perhaps hinting at the sense of scale for this giant world

Jupiter is gradually becoming more prominent in the pre-dawn sky, and if early reports from dedicated Jove-watchers indicate anything about this year’s apparition it is going to be a very interesting year to watch the giant planet.  Usually the planet’s disc is dominated by two prominent dark equatorial cloud belts, but as Old Jove has emerged from morning twilight it appears that the South Equatorial Belt has completely disappeared!  While these fadings of the SEB are unusual, they are not unprecedented and may reflect seasonal effects in the planet’s atmosphere that vary on a decadal scale.  One boon to observers is that this dramatic fading now means that the Great Red Spot stands out more prominently, so hopefully many new observers will get to know this mysterious and famous feature in the months to come.

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