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The Sky This Week, 2011 April 26 - May 3

"May"-hem on May Day, later "early" evenings, and happenings at dawn.
Saturn, imaged 2011 APR 22, 03:05 UT
at the E.W. Rice Observatory, Fishers Island, NY

The Moon wanes through her crescent phases in the early morning skies this week. New Moon occurs on May 3rd at 2:51 am Eastern Daylight Time. Luna spends most of the week among the star-poor reaches of the rising autumnal constellations, but from the 29th through May 1st she shares the gathering morning twilight with the bright glow of brilliant Venus. The best time to look for this duo is about half an hour before sunrise, just above the eastern horizon.

May 1st is one of the ancient seasonal markers that were once widely observed throughout Celtic and medieval Europe. Now widely observed as "May Day", an international workers’ holiday, its origins date back well over a thousand years. Celtic societies knew it as "Beltaine" a celebration of the opening of the agricultural planting and breeding season and the end of boreal winter. It was celebrated by huge bonfires and much merry-making, with attendant May-poles, May Queens, and general "mayhem". May Day is one of the so-called "cross-quarter" days that mark the mid-points of the astronomical seasons. The four seasonal markers and four cross-quarter days were the traditional dates when serfs paid their rent to their feudal masters in medieval times. We still unwittingly observe three of the four cross-quarter days in modern times. In addition to May Day, the old Celtic observance of Samhain is now celebrated as Halloween, and Imbolc is now observed as the Christian Candlemas or secular Groundhog Day. The fourth cross-quarter day, Lughnasadh, falls on August 1st, and is still observed in a few locations in Scotland as "Lammas". Whatever the origins, May Day is still a time to celebrate the rebirth of spring as new leaves green the trees and new life emerges in field and forest.

The idea of "early evening" is now becoming something of a misnomer. The Sun sets at 8:00 pm on April 30th, and a minute later on each succeeding night. This means that the end of evening astronomical twilight doesn’t fall until after 9:30 pm, so if you want to enjoy dark-sky viewing of faint star clusters, galaxies and nebulae be prepared to stay up until the wee hours. This is actually a great time of year for galaxy-hunting with a telescope from a dark-sky location. The area of the sky loosely bounded by Leo, the Bid Dipper, and the stars Arcturus and Spica is home to the central mass of the Virgo Galaxy Cluster, of which our Milky Way is a far-flung outlier. You can almost randomly point a six-inch or larger telescope at any spot in this part of the sky and find a faint fuzzy blob of light looking back at you. There are some areas where up to a dozen of these vast, distant stellar cities can be seen wafting through an eyepiece field. William Herschel, the great 18th Century English astronomer, identified over 350 galaxies in the constellation Virgo alone with his 18-inch aperture metal-mirror reflecting telescope!

If you tire of hunting down faint smudges or just don’t feel like traipsing out of the city, Virgo also hosts the evening’s only bright planet, Saturn. Best known for his spectacular rings, Saturn is also a treat for medium- to large-aperture scopes thanks to his flock of moons. Most of these worlds are small spheres of solid water ice, but the brightest, Titan, has a dynamic atmosphere with active weather that rains liquid methane to a surface covered with lakes of exotic organic compounds and boulders of water ice.

In addition to the waning Moon and Venus, viewers of the pre-dawn sky should get ready for the reappearance of Mercury and Jupiter from solar conjunction. If you have a clear eastern horizon there will be a veritable traffic jam of planets there next week!

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