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Snow tree

Photo of the Week. May winter be but a memory.

Astronomy news for the week starting Friday, April 15, 2011.

The week begins with the Moon in its waxing gibbous state which develops to full the night of Sunday, April 17th, after which it fades in the waning gibbous, third quarter not reached until the night of Sunday the 24th. The night of Friday the 15th sees the growing Moon well to the west of Saturn, while the following night look for the rising Moon to be to the right of the ringed planet, conjunction with the Moon (the planet 8 degrees to the north) taking place around midnight the night of Saturday the 16th.

A day before full phase, the Moon once again passes perigee, where and when it is closest to Earth, closely replicating last month's "supermoon," when the Moon was supposed to be "huge," brighter and larger than normal. While the statement was (and remains) technically true, the differences caused by changes in lunar distance are not really noticeable to the naked eye. That the full Moon appears especially large when rising is a well-known, though not well-understood, optical illusion that holds for the Sun (when comfortably dimmed) and constellations as well.

This week also starts us off with a series of planetary conjunctions as a result of much of the Sun's family being bunched in the morning hours, though all are difficult, if not impossible, to see. But out of general interest, Mercury passes less than a degree north of Mars on the morning of Tuesday the 19th, followed by Venus visiting with Uranus on Friday the 22nd. The only perfectly visible planet, however, remains Saturn, which, having passed opposition with the Sun early in the month, now rises before sunset, making it nicely visible in the east (still to the northwest of Spica) by the time the sky darkens enough to see the stars. Saturn then crosses the meridian at midnight Daylight Time, and sets in morning twilight. Still, though low, Venus is so bright that it remains visible shortly before sunrise.

The morning of Friday the 22nd marks the peak of the Lyrid meteor shower, which in a dark sky can yield 10-20 meteors per hour (and sometimes many more) that appear to emanate from the constellation Lyra, which is marked by bright Vega. Unfortunately, the waning gibbous Moon will get in the way. The meteors are the leavings of Comet Thatcher, which, with its period of 415 years, last returned in 1861.

As Saturn and Spica creep across the sky, they make an almost instantly recognizable couple. Look then to the southwest of Spica (the southeastern of the Saturn-Spica pairing) to find (once the Moon is out of the way) the distorted box that makes Corvus, the Crow, or Raven, its top two stars pointing right back at Spica. For a challenge, to the west of Corvus is dim but ancient Crater, the Cup, which sits on the back of Hydra (the Water Serpent) and really does rather look like what it is named for.
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