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Windswept clouds

Photo of the Week. Perhaps the lovely windswept cirrus will blow away to give us a clear night.

Astronomy news for the week starting Friday, May 4, 2007.

The Moon having passed full last May 2, the night skies begin to darken once again, though it will be later in the week before we see any real difference. At first the Moon will wane through its gibbous phase, then pass third quarter the night of Wednesday the 9th, roughly about the time of Moonrise in North America. With the Sun now halfway to the Summer Solstice, the third quarter, 90 degrees "behind" (to the west of) the Sun, will shine among the dim stars of Capricornus. In what is left of the remainder of the week, the Moon will wane as a fat crescent. Look the morning of Saturday the 5th to see the gibbous Moon passing some 6 degrees to the south of Jupiter. Even people familiar with the sky tend to lose sight of the third dimension. While Jupiter and the Moon seem painted on the dome of the sky, they are at vastly different distances, the Moon a mere quarter million miles (or so) away, Jupiter 1500 times farther! On the morning of Thursday the 10th, the Moon then takes on much dimmer and more-distant Uranus (which is at the moment 4.6 times farther than Jupiter).

Evening's Venus rises yet higher and sets yet later in the northwest, as it does not finally go down until just after 11:30 PM Daylight Time, the planet giving us one of the best apparitions possible. Venus has a long-term, eight year, cycle in which it repeats its apparitions. That is, in 1999 it appeared much as it does now, while in 2015 you'll see much the same again. This brightest of the "ancient planets" is now nicely paired with the faintest, Saturn . Slowly approaching each other, they are heading for a very nice conjunction on July 1, when they will be just under a degree apart. In western skies to the west of Leo, the ringed planet remains up until 2:30 AM, setting about half an hour before Jupiter (now rising at 10:30 PM) crosses the meridian.

Lying between classical Scorpius and Sagittarius, Jupiter is actually moving slowly against the background of the "13th constellation" of the Zodiac, Ophiuchus. Very much NOT part of the classical Zodiac, the modern (and arbitrary) boundaries of the giant constellation cut across the ecliptic. The Sun is actually "in Ophiuchus" (roughly November 30 to December 18) for longer than it is "in Scorpius" (November 24 to 30).

As we move into May, Mars slowly begins to break away from twilight. Though still elusive, the red planet is at least rising almost half an hour before the onset of dawn.

Sunday the 6th marks the peak of the Eta Aquarid meteor shower (named after a star close to the apparent radiant from which the meteors seem to come). But don't bother looking. The meteors from the debris of Halley's Comet are few and far between and will be wiped out by a nearly full Moon.

Here comes Centaurus. The giant constellation is now making serious inroads into the far southern sky. Look far to the south down below Virgo's Spica to find its very top stars, which will be skirting the horizon for middle North America, its two luminaries Rigil Kentaurus (Alpha Centauri, the closest star to Earth) and Hadar (Beta), far out of sight except for far southern latitudes.
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