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Winter sunrise

Photo of the Week. Winter Sunrise

Astronomy news for the week starting Friday, January 18, 2008.

Skylights now resumes its normal weekly schedule.

The Moon passes through full phase this week, just after moonset on Tuesday, January 22, when its brightness (30,000 times that of Sirius, the brightest star) blots out the fainter stars. Since the full Moon is lit by the Sun directly from the front, the lack of shadows makes telescopic lunar features hard to discern. Earlier in the week, the Moon fattens in the waxing gibbous phase, while afterward it wanes in the gibbous. Our week begins with the Moon near perigee, where it is closest to the Earth.

The evening of Saturday the 19th, the Moon and Mars will get together, the Moon passing just to the north of the red planet, which will be occulted as seen from the Arctic. Then look for the Moon to the west of Regulus in Leo the night of Wednesday the 23rd. The night of Thursday the 24th, the Moon will be to the east of the star and will pass just a few degrees to the south of Saturn.

Mars, in retrograde motion in northeastern Taurus just south of Auriga, dominates the nighttime sky. Transiting high across the meridian around 9:30 PM, the neighborly planet does not set in the northwest until 5 AM, about the time our other neighbor, Venus, rises in the southeast. Though dropping ever lower in the morning sky, Venus still rises over half an hour before dawn announces the coming rising of both Jupiter (around 6 AM, difficult to see) and the Sun (pretty obvious). Still between them is slowly moving Saturn, which rises in Leo to the southeast of Regulus about 8 PM, and transits the meridian around 2:30 AM. Back to the evening, the news is mostly of Mercury, which makes a brief appearance in southwestern twilight skies, as it hits greatest eastern elongation the night of Monday the 21st.

Though bright moonlight will block out much of the stellar sky, it will still be easy to find bright Orion and company. Look to the southwestern corner of the Hunter, to southwest of the three-star belt, to locate bright blue-white Rigel. Just to the northwest of Rigel lies third magnitude Cursa, which marks the beginning of the River Eridanus. The celestial stream then flows some thirty degrees to the west before its rapids plunge south, and for northerners below the horizon, where they end in bright, first magnitude, Achernar, which lies only about 33 degrees from the South Celestial Pole.
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