Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9 -- Full List Restored!


Photo of the Week. Cloudscape from on high.

Astronomy news for the week starting Friday, December 4, 2009.

Skylights now resumes its normal weekly schedule.

The Moon is making its late rounds this week. Having passed full at the beginning of the month, it starts us off in its waning gibbous phase as it heads towards third quarter, which takes place the night of Tuesday, December 8, before Moonrise in North America. Though the same amount of the Moon is visible at first quarter as at third, the third is only half as bright as the first as a result of its having more dark maria, or lava flows, upon it. The Moon then spends the remainder of the week in the waning crescent, which thins as morning-to- morning it descends to the eastern horizon.

As our lunar companion treads its path, it will appear to the west of Mars the night of Saturday the 5th, and will then pass nicely to the south of the red planet (the reddish color coming from iron oxides in the surface "soil") the night of Sunday the 6th. A few days later, on the morning of Thursday the 10th, the Moon will then pass well to the south of Saturn.

Jupiter makes something of a transition this week as it crosses the meridian at sunset and thus appears to the west of the north-south line when it becomes visible at dusk. It then sets early, just after 9:30 PM. Half an hour before, however, Mars rises (its rising time getting rapidly earlier), and then transits the meridian an hour before dawn begins to light the sky. Then we stay in the morning skies with the rising of Saturn around 1 AM. The sight at 5 AM is glorious, with Castor and Pollux, Mars, Regulus, Saturn, and Spica all in a row cascading from northwest to southeast along the ecliptic.

The inner planets, however, are effectively gone from us. In the morning, Venus now rises just half an hour before sunrise, and in the evening, Mercury, while climbing slowly out of dusk, is not yet high enough to see.

It's the Sun itself that makes a bit of a splash. As a result of the eccentricity of the Earth's orbit and the tilt of the rotation axis, the earliest sunset takes place on December 7, two weeks before the shortest day. Watch then as the evenings begin to get lighter.

The Sea Monster is upon us. Follow the left side of the Great Square of Pegasus downward to rather bright Deneb Kaitos, Beta Ceti, the tail of Cetus the Whale. The rest of the constellation spreads up and to the left (to the left of southern Pisces) to the ragged circle of stars that marks the Monster's head. Along the way lies Mira, "the Wonderful," one of the classic variables of the sky. Can't find Cetus? Wait for the rising of more obvious Taurus. The Bull's vee-shaped head points directly at the Whale's head, each of the two beasts seen as rather contemplating what the other one is all about.
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