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The Sky This Week, 2012 May 29 - June 5

Venus' Last Stand

Venus, imaged with the U.S. Naval Observatory's 12-inch (30.5-cm)
f/15 Clark/Saegmüller refractor, 2102 May 29, 18:26 UT

The Moon waxes to the Full phase this week, adding her glow to the warm nights of late spring. June’s Full Moon occurs on the 4th at 7:22 am Eastern Daylight Time. The popular names for this particular Full Moon are the Flower Moon, Rose Moon, Strawberry Moon, or Honey Moon. These names all derive from Luna’s appearance in the late-night Northern Hemisphere sky. Since the Moon’s path along the Ecliptic takes her to her most southerly excursion of the year, her light is scattered by more particles in the atmosphere, giving her a somewhat "warmer" tone since air molecules preferentially scatter blue light. Early risers in the western parts of the U.S. may also see a ruddy "bite" taken out of Luna’s disc shortly before she sets. This partial lunar eclipse will hide about 37% of the Moon’s face at mid-eclipse, which occurs at 6:04 am CDT (5:04 am MDT, 4:04 am PDT). Look for Luna a mere two degrees below the bright star Spica on the evening of the 31st. On June 3rd she passes four degrees north of ruddy Antares, lead star of Scorpius, the Scorpion.

The biggest astronomical event of the year is now just about upon us. The Transit of Venus will occur on the 5th starting at 6:04 pm EDT here in Washington when a tiny "notch" will begin to appear on the Sun’s northeastern limb. The notch will grow into a small black disc that will be completely projected upon the Sun by 6:22 pm. Over the next six and a half hours the dark orb of Venus will make its way across the Sun, emerging off Old Sol’s limb for observers in most of Europe, eastern Africa, and Asia. Residents of the Pacific Rim will see the transit in its entirety. While this isn’t exactly a visually stunning event like a total solar eclipse, it is nonetheless a literal "once-in-a-lifetime" event (or twice if you saw the Transit of 2004!) The next Transit of Venus won’t occur for another 105.5 years and that one, scheduled for December 11th 2117, won’t be visible at all from the Washington area! Needless to say, looking at an event that involves direct viewing of the Sun requires the utmost care and safety to view safely. Looking at the Sun directly can and will cause permanent eye damage, so please make sure that you take the proper precautions. If you are viewing directly with the naked eye use at least a #14 welder’s glass filter or a proper "white light" telescope filter. You can safely project the Sun’s image through a single element of a pair of binoculars or a small telescope onto a sheet of paper. Your best bet is to find out where local amateur astronomers will be viewing the event. Of course, if it’s cloudy all bets are off and you’ll have to wait until 2117!

Early in the week you may still be able to catch a fleeting glimpse of Venus very shortly after sunset on the west-northwest horizon. You will need to have a wide-open view in this direction and a clear evening as well. Venus sets about eight minutes earlier each night this week. What’s the date when you catch your last glimpse of her?

Mars tacks on another three degrees of separation from the bright star Regulus in the constellation Leo this week. The red planet will continue this steady eastward march for the rest of the calendar year. Currently shining at a magnitude of 0.5, he is still the brightest and ruddiest star-like object in this part of the sky. The apparent diameter of his disc shrinks to below eight arcseconds this week, making detail on his distant face hard to pick out in all but the largest of telescopes.

Saturn is far and away the best planet for evening observing now. He crosses the meridian at around 10:00 pm, at which time the sky should be almost fully dark. Small telescopes will have no trouble showing the planet’s fascinating rings, and larger telescopes will show many of his enigmatic moons. Titan, the largest of these distant attendants, is bright enough to be seen in a 60mm glass, but an 8-inch (200mm) objective will reveal up to five more on a clear and steady night.

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