Friday, 28 December 2012

Last full moon of 2012 on December 27-28

Your calendar probably says tomorrow (Friday, December 28) is the date for the last full moon of 2012. But, for North America, the full moon comes before sunrise tomorrow. So, for us, the moon is closer to full tonight than tomorrow night. Need the exact time of full moon? It’s Friday, December 28 at 10:21 UTC (5:21 a.m. EST, 4:21 a.m. CST, 3:21 a.m. MST and 2:21 a.m. PST). Seeing a bright object in the moon’s vicinity? It’s Jupiter.

Day and night sides of Earth at instant of full moon

Earth’s day and night sides at instant of full moon (2012 December 28 at 10:21 UT). Image credit: Earth and Moon

You might have noticed that the moon was closer to Jupiter yesterday, on December 26, and closer yet on December 25. As always, the moon moves eastward in front of the backdrop stars (and planets) as its orbits our planet Earth. That eastward motion of the moon in orbit causes the moon to moves eastward on our sky’s dome from night to night.

Because this is the closest full moon to the December solstice, this moon carries the name Long Night Moon. That name works for the Northern Hemisphere, where the daylight is fleeting now, while the nighttime is long-lasting. In the Southern Hemisphere – where the days are long and the nights are short – perhaps we could call the closest full moon to the December solstice the Short Night Moon.

Full moon December 27-28, 2012 as seen from Hong Kong by EarthSky Facebook friend Rocco Sung. Thanks Rocco!

The full moon – as always – mimics the sun’s path for some six months hence. Watch tonight as the moon rises around sunset and sets around sunrise tomorrow. Around midnight, the moon climbs highest up for the night, mimicking the position of the noonday June solstice sun.

Given clear skies, tropical and temperate regions from all around the world will see the moon shining from dusk until dawn tonight. In the Northern Hemisphere, the moon’s path across the sky tonight will resemble that of the high-flying summer solstice sun. In the Southern Hemisphere, the moon’s path will follow the low arc of the sun on the winter solstice.

North of the Arctic Circle, there is no sunrise right now because the sun stays below the horizon. But the closest full moon to the December solstice stays out all night long at these far northern latitudes, playacting as the midnight sun of summer.

South of the Antarctic Circle, the sun stays out for 24 hours around the clock. However, the closest full moon to the December solstice simulates the winter sun in the Southern Hemisphere. For that reason, this December full moon won’t rise above the horizon at these far southern latitudes.

The Winter Circle as seen from the Northern Hemisphere

By the way, tonight’s bright and round moon shines right in front of the great big star formation known as the Winter Circle. In the Southern Hemisphere, though, it should really be called the Summer Circle. Either way, tonight’s moon shows you where the sun will reside in front of the background stars six months from now.

Year after year, the Winter Circle shines way high at midnight around the time of the December solstice. However, the presence of the brilliant planet Jupiter near the Winter Circle star Aldebaran is special to this year. You simply can’t miss this dazzling planet, as it’s even brighter than Sirius, the brightest star of the nighttime sky. So let the full moon guide you to Jupiter, the brightest star-like light in the evening sky. Then use Jupiter to find the star Aldebaran and the other bright stars of the Winter Circle.

The Winter Circle as seen from the Southern Hemisphere

Watch tonight, as the Northern Hemisphere’s Long Night Moon (Southern Hemisphere’s Short Night Moon) lights up the nighttime from dusk till dawn!


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