Half-Moon Makes Dramatic Pass at Uranus TonightThe half-moon will pass very close to the planet Uranus for skywatchers across North America this evening Sunday, Dec. 28th. Pop the rubber lens caps off those binoculars and point them at the Moon. If you look a short distance to the left you’ll notice a star-like object. That’s the planet!
You can do this anytime it’s dark, but the later you look the better because the Moon moves eastward and closer to the planet as the hours tick by. Early in the evening, the two will be separated by a couple degrees, but around 11:30 p.m. CST (9:30 p.m. PST) when the Moon reclines in the western sky, the planet will dangle like an solitary diamond less than a third of a lunar diameter away. When closest to the Moon, Uranus may prove tricky to see in its glare. If you hide the Moon behind a chimney, roofline or power pole, you’ll find it easier to see the planet.
The farther north you live, the closer the twain will be. Skywatchers in Japan, the northeastern portion of Russia, northern Canada and Alaska will see the Moon completely hide Uranus for a time. The farther west you are, the higher the Moon will be when they conjoin. West Coast states see the pair highest when they’re closest, but everyone will get a good view.
When closest, the radically different character of each world can best be appreciated in a telescope. Pump the magnification up to 150x and slide both planet and Moon into the same field of view. Uranus, a pale blue dot, wears a permanent cover of methane-laced clouds where temperatures hover around -350°F (-212°C).
The fantastically large-appearing Moon in contrast has precious little atmosphere and its sunny terrain bakes at 250°F (121°C). And just look at those craters! First-quarter phase is one of the best times for Moon viewing. The terminator or shadow-line that divides lunar day from night slices right across the middle of the lunar landscape.
Shadows cast by mountain peaks and crater rims are longest and most dramatic around this time because we look squarely down upon them. At crescent and gibbous phases, the terminator is off to one side and craters and their shadows appear scrunched and foreshortened.
Enjoy the tonight’s conjunction and consider the depth of space your view encompasses. Uranus is 1.85 billion miles (2.9 billion km) from Earth today, some 7,700 times farther away than the half-moon.