Monday, December 12
Tonight’s nearly Full Moon passes in front of (occults) the 1st-magnitude star Aldebaran for observers across most of the United States and Canada. As darkness falls, you’ll see Earth’s only natural satellite suspended against the stars of the Hyades, the cluster that forms the face of Taurus the Bull. As the evening wears on, the Moon edges closer to Aldebaran. The occultation occurs at roughly midnight EST on the East Coast but closer to 8 p.m. PST on the West Coast. Binoculars or a telescope will deliver the best views of this dramatic event.
If the Moon looks a little bigger than normal set against the Hyades star cluster, it may not be your imagination. Luna reaches perigee, the closest point in its orbit around Earth, at 6:29 p.m. EST. It then lies 222,737 miles (358,461 kilometers) away from us.
Tuesday, December 13
Full Moon officially arrives at 7:06 p.m. EST, but it looks completely illuminated all night. You can find it rising in the east just after sunset and peaking in the south around midnight local time. It dips low in the west by the time morning twilight begins. The Moon lies in southeastern Taurus during the evening hours but crosses into northern Orion before daybreak.
The annual Geminid meteor shower reaches its peak this evening. Unfortunately, the Full Moon shares the sky with the meteors and will drown out the shower’s fainter members. Under clear skies, attentive observers could see perhaps 10 to 15 meteors per hour. Your best option is to observe from a rural location, where the lights of the city won’t add to the Moon’s glow.
Wednesday, December 14
If it weren’t for the presence of a bright Moon, Jupiter would dominate the morning sky. The giant planet rises around 2 a.m. local time and climbs 35° above the southeastern horizon by the time twilight begins. Jupiter shines brilliantly at magnitude –1.8 and shows a 34"-diameter disk when viewed through a telescope. A small scope also reveals the planet’s four bright moons, though you may have to hunt for two of them this morning. Giant Ganymede transits Jupiter’s north polar region beginning at 2:40 a.m. EST. While only those in eastern North America can see the transit’s start, nearly everyone can witness its finish at 5:08 a.m. Io’s shadow begins a transit just seven minutes later, at 5:15 a.m., followed by Io itself at 6:21 a.m.
Thursday, December 15
Head outside in early evening this week and you can see the Big Dipper scraping the northern horizon. For latitudes north of about 40°, this conspicuous asterism never rises or sets (“circumpolar” in astronomical parlance), though December evenings find it at its lowest ebb. This means that the constellation on the opposite side of the North Celestial Pole, the familiar W-shaped Cassiopeia, currently rides highest in the sky.