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The Sky This Week, 2014 May 6 - 13

Five planets in one night.
The Moon and Mercury, 2014 February 1
Imaged from Alexandria, Virginia

The Moon brightens the evening sky this week, waxing from First Quarter to Full as she passes through the constellations of spring.  Full Moon occurs on the 14th at 3:16 pm Eastern Daylight Time.  May’s Full Moon is variously known as the Grass Moon, Milk Moon, Flower Moon, or Corn Planting Moon.  Luna passes six degrees south of the bright star Regulus in Leo, the Lion on the evening of the 7th.  On the 10th and the 11th you’ll find her in the company of ruddy Mars; on the latter night she is located a few degrees west of the bright star Spica as well.  By the week’s end she is closing in on yellow-hued Saturn low in the southeastern sky as twilight ends.  If you look at her with binoculars on that night you’ll find her less than half a degree north of the second-magnitude star Zubenelgenubi, the brightest star in the constellation of Libra, the scales.

This is one of those rare weeks when you have an opportunity to see all of the planets known to the ancients during the course of the night.  Four of them are well-placed for viewing before midnight, while the fifth can be seen just before sunrise.  The evening show begins with the appearance of Mercury, which owns the dubious distinction of being the most difficult of these worlds to observe.  Fortunately for us the fleet planet is beginning his best evening apparition of the year, and he should be fairly easy to spot from about May 10th until early June.  Mercury seems to leap up from the horizon this week as evening twilight deepens.  If you have a flat western horizon start looking for him on the 10th at around 9:00 pm.  He’ll be about five degrees above the horizon that evening, glowing at a respectable -1 magnitude.  He gains about a degree per day in altitude with each successive evening, becoming more prominent above the horizon haze.  He’ll continue to climb until he reaches elongation on the 25th, so you should have plenty of time to get him in your sights.  Binoculars will often help to locate him in brighter twilight, but once you’ve found him he should be an easy naked-eye target.

The next planet you’ll encounter is giant Jupiter, who pops out of evening twilight in the western sky shortly after sunset.  Old Jove remains the brightest planet in the evening sky so you should have no trouble identifying him.  A quick view with binoculars should reveal various combinations of his four bright Galilean moons.  Jupiter has been providing us with some great telescopic views since the beginning of the year, but he’s now beginning to sink into the turbulence of the atmosphere above the horizon.  His apparent disc is now about three-quarters the size that it was at opposition in January, so it’s becoming increasingly difficult to spot fine structure in his atmospheric cloud belts.

As Jupiter heels over toward the west, Mars makes his move toward the meridian.  This planet is also pretty hard to miss thanks to his distinct rosy hue.  By 10:30 he’s nearing his highest altitude of the evening, beckoning modest telescope owners for a look.  While his apparent disc is less than half the size of Jupiter’s, he has one distinction that sets him apart from all of the other easily observable planets.  When you eke out details in moments of good seeing, you’re looking at a solid surface rather than the tops of dense atmospheres.  This has tantalized observers since the invention of the telescope and is still a source of fascination today.  You should be able to see the small white north polar ice cap in moments of steady air, and whitish patches near the center of the disc are water-ice clouds forming around a large volcano in a region called Elysium.

Saturn reaches opposition on May 10th, rising at sunset and remaining in the sky until dawn.  Saturn can be a welcome respite for those who’ve spent long hours trying to view small details on Mars.  Yes, the details on Saturn’s globe are quite subtle, but the overall appearance of the planet is anything but.  This planet is probably the most unusual sight a novice can see through a telescope, and the first view that someone has of Saturn spinning inside its rings invariably brings reactions of incredulity.  We now know that the rings are composed of countless icy bodies ranging in size from dust grains to hundreds of meters across, each in an independent orbit around the planet itself.  Saturn will be spending the rest of the spring and early summer with us, so you’ll have plenty of chances to get a good view.

Our last planet has also been with us in the morning sky since the beginning of the year.  Bright Venus is usually very well-placed in our skies, but this year she’s being shy for northern hemisphere observers.  You’ll find her in the gathering morning twilight just above the eastern horizon. 

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