Skylights featured on Astronomy Picture of the Day

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Skylights featured five times on Earth Science Picture of the Day:
1 , 2 , 3 , 4 , 5

Silver linings

Photo of the Week. Silver linings bring peace to a turbulent sky.

Astronomy news for the week starting Friday, December 9, 2005.

The Moon, having passed first quarter last Thursday, December 8, grows through its waxing gibbous phase toward full, that phase reached at the end of Skylights' week on Thursday the 15th during daylight morning hours in North America. The night of Wednesday the 14th, the Moon will therefore rise not quite full just before sunset, whereas the following night it will rise just after sunset and just past full.

Speaking of which, the earliest sunset took place around December 7. Even though the days will keep getting shorter until the passage of the Sun across the Winter Solstice in Sagittarius on December 21, the Sun will begin to set later, the difference compliments of the tilt of the Earth's axis and the eccentricity of its orbit.

The week is filled with planetary events. Topping the list, Venus hits its greatest brilliancy for this current orbital pass on Friday the 9th. Though presenting mostly its nighttime side in a distinct crescent phase (visible only telescopically), the planet is so close to us (60 million kilometers, 38 million miles) that it is still 18 times brighter than the brightest star, Sirius. Though at the beginning of the week not setting until around 7:30 PM, Venus will from here on out quickly disappear, by the end of the year setting an hour earlier, just as twilight ends. On the other side of the sky and the night, Venus's brother planet Mercury is for now at its best, reaching greatest western elongation (21 degrees to the west of the Sun) on Monday the 12th and rising in the east- southeast just as dawn breaks. If you cannot find Mercury, you surely can admire very bright Jupiter, which at dawn dominates the southeastern sky, the king of the planetary system now rising around 4 AM well to the east of Spica.

In between are Mars and Saturn. The ringed planet (in Cancer) now rises in mid-evening, around 8:30 PM, just half an hour before Mars (in Aries) transits the meridian to the south. Mars then sets as Jupiter rises. As the Earth pulls away from it, Mars is fading some, and ceases retrograde motion on Saturday the 10th. The following night, the the Moon will encroach upon it from the west. If it is not cold enough for you here, the Moon will occult Mars as seen from northeastern Siberia.

Keep your eye out for meteors from the Geminid shower (the debris of the defunct comet 3200 Phaeton), which peaks the morning of Tuesday the 13th. The bright Moon will unfortunatly blot out much of the show.

The autumn stars begin to slip away. By mid evening, the Great Square of Pegasus is to the west of the meridian, while to the southeast of it, Pisces (hardly visible in bright moonlight) straddles it. To the southeast of Pisces, Cetus the Sea Monster swims the mythical seas, while farther down in the same direction winds Eridanus, the River, which ends far to the south in the bright blue star Achernar.
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