The Sky This Week from December 6 to 15 – Astronomy Magazine

Friday, December 6A lone bright star now hangs low in the south during early evening. First-magnitude Fomalhaut often called the Solitary One belongs to the constellation Piscis Austrinus the Southern Fish. From mid-northern latitudes, it climbs 20 above the horizon at its best. How solitary is Fomalhaut? The nearest 1st-magnitude star to it, Achernar at the southern end of Eridanus the River, lies some 40 away.

Saturday, December 7The variable star Algol in Perseus reaches minimum brightness at 7:07 p.m. EST, when it shines at magnitude 3.4. If you start watching it after darkness falls this evening, you can see it more than triple in brightness, to magnitude 2.1, over the course of a few hours. This eclipsing binary star runs through a cycle from minimum to maximum and back every 2.87 days. Algol appears in the northeastern sky after sunset and passes nearly overhead around 10 p.m. local time.

Sunday, December 8Although people in the Northern Hemisphere wont experience the shortest day of the year for another two weeks (at the winter solstice December 21), those at 40 north latitude will see the Sun set earlier today than at any other time this year. Tomorrows sunset will arrive about two seconds later and, by the solstice, our star will set three to four minutes later than today. The date of earliest sunset depends on latitude the farther north you live, the closer it occurs to the solstice.

Monday, December 9Uranus reached opposition and peak visibility in late October, but it remains a tempting target in December. The outer planet appears in the southeastern sky after darkness falls and climbs highest in the south around 9 p.m. local time. The magnitude 5.7 world lies in southwestern Aries the Ram, near that constellations border with Pisces the Fish and Cetus the Whale. Although Uranus shines brightly enough to glimpse with the naked eye from a dark site, youll need binoculars to locate it this week with a gibbous Moon sharing the sky. The closest guide star is magnitude 4.4 Xi1 (1) Ceti, which lies 4 to the southeast. A telescope reveals Uranus disk, which spans 3.7" and shows a distinct blue-green hue.

Tuesday, December 10Venus gleams in the southwestern sky after sunset. The brilliant planet stands out just a half hour after sunset, when it appears 15 above the horizon. Wait another 30 minutes and you should see magnitude 0.6 Saturn just 1.8 to Venus north (upper right). Although magnitude 3.9 Venus stands out to the naked eye, binoculars deliver the best views of the pretty conjunction. Target the planets individually through a telescope and youll see Venus 12"-diameter disk and 87-percent-lit phase, as well as Saturns 15"-diameter globe surrounded by a ring system that spans 35".

The nearly Full Moon sits among the background stars of Taurus the Bull early this evening, just west of the Hyades star cluster. As the night wears on, Earths only natural satellite slides through the northern fringes of this V-shaped star group. The conjunction affords a good opportunity to witness the Moons motion.