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Clear Day

Photo of the Week. A clear day, light clouds stretching out to the horizon, gives hope for an especially starry night.

Astronomy news for the week starting Friday, January 12, 2007.

Nearly the entire week is spent with the Moon in its waning crescent phase, allowing for dark evening skies, new Moon not reached until the night of Thursday, January 18. Early in the week the Moon makes a series of passages. An especially nice one will occur the morning of Monday the 15th when it will be seen just barely to the south of Antares in Scorpius with Jupiter several degrees up and to the left of the pair, the sight well worth getting up early for. (The Moon will occult Antares as seen from southern Africa, South America, and Antarctica.) The following morning, that of Tuesday the 16th, you will find the Moon almost immediately to the right of Mars.

With Jupiter now rising just after 4 AM, well before the onset of twilight, it is easy to find, indeed impossible not to, as by late twilight it is well up in the southeast. Mars is a different matter. Though just over the line into first magnitude, it is still much fainter than Jupiter. Moreover its rising closely tracks the onset of dawn, and will continue to do so until the end of April, making it rather difficult to see in growing morning twilight. With the Sun now rising ever later as winter creeps slowly toward spring, you'll have to look ever earlier to spot the red planet.

While the morning holds Jupiter and Mars, the evening rather symmetrically hosts Saturn and Venus. Saturn, rising just after 7 PM to the west of Regulus in Leo, is then up the rest of the night, crossing the meridian to the south around 2 AM. By dawn it lies well into western skies. Venus, easily visible in bright southwestern twilight, now makes something of a transition, as around Thursday the 18th it finally sets just as twilight ends. That same day, Venus passes 1.4 degrees south of Neptune, a passage appreciated only in thought, as it will be impossible to see.

Comet McNaught, which became unexpectedly bright, is now out of sight for northerners as it plunges into the southern hemisphere.

The charm of the nighttime sky lies not just in its classic constellations but also in smaller informal figures or "asterisms." Among the most beloved are the Big Dipper of Ursa Major, Ursa Minor's Little Dipper, Orion's Belt and Sword, the Hyades and Pleiades carried by Taurus, the Sickle of Leo, the three "Kids" of Auriga, and now slipping away to the west, the Circlet of Pisces and the Water Jar of Aquarius.
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