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Winter sunset

Photo of the Week.Winter sunset.

Astronomy news for the two weeks starting Friday, December 5, 2014.

The next Skylights will appear Friday, December 19.

It's yet another two-weeker and it's jammed full of good stuff. We begin just shy of full Moon, which is passed the morning of Saturday, December 6, near Moonset in North America. Look near dawn for it glowing above the northwestern horizon. We then swing through the waning gibbous phase, third quarter on Saturday the 14th near sunrise, and finally through a good portion of the waning crescent. The evening of Friday the 5th, the Moon plows through the Hyades star cluster in Taurus, which because of the lunar brightness will be hard to see, though you may spot Aldebaran (which is not actually a member of the cluster). The Pleiades will be northwest of them. Then look the night of Thursday the 11th to see the Moon passing five degrees south of Jupiter, while the following night it will make a fine triangle with Jupiter and Regulus in Leo. At the end we see the crescent bearing down on Saturn the morning of Friday the 19th. The Moon passes apogee, where it is farthest from Earth, in the middle of our fortnight, on Friday the 12th.

Jupiter remains ascendant, rising before 10 PM as we begin our period, shortly before 9 by the end of it. It crosses the celestial meridian to the south just before dawn. The giant planet ceases its direct motion against the stars of Leo to the west of Regulus on Tuesday the 9th, whence it begins its westerly retrograde trek. Mars, climbing through Capricornus, continues its 8 PM setting time as it slowly falls behind the Earth. Returning to the scene, Saturn clears the start of twilight shortly after we began this tale northwest of the three-star head of Scorpius. Not that anybody will notice, but Mercury passes superior conjunction with the Sun (on the other side of it), on Monday the 8th. You won't see it again until 2015. Venus, however, is slowly becoming visible within evening twilight. And because of Earth's axial tilt and orbital eccentricity, the earliest sunset as seen from mid-northern-latitudes arrives on Monday the 7th. By the time of the start of winter (and shortest day) on December 21, the evening sky is notably lighter.

One of the better and more interesting meteor showers, the Geminids, peaks the morning of Saturday the 14th. Capable of more than a meteor a minute, the shower will be marred by a quarter Moon. The Geminids are the debris of Comet 3200 Phaeton. Once thought to be an asteroid, Phaeton orbits the Sun in a short period of just 1.43 years and comes well inside the orbit of the Earth (but does not intersect us).

Right in the middle of things, in early evening find the Great Square of Pegasus high to the south, Andromeda streaming off its upper left corner. Then around midnight climbs one of the great glories of the sky, Orion, the Hunter, with his silvery three-star belt and the magnificent red supergiant Betelgeuse at the upper left. Wait a bit then to see the rising of brilliant Sirius, the brightest star of the sky.

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