
December 21st marks the Winter Solstice, that brief moment in the Earth year when our planet's axial tilt is farthest from the Sun. It's also at this point that the pattern of shortening days and longer nights begins it slow reversal.
In Northern climates, this is a welcome milestone on the calendar and various cultural observances have been held over the millenia to mark the occasion.
This year is extra special as the Solstice will coincide with both a full Moon and a total lunar eclipse. A lunar eclipse only occurs when the Sun, Earth and Moon are aligned exactly, or very closely so, with the Earth in the middle, blocking the Sun's light onto the Moon. For this reason, there is always a full Moon the night of a lunar eclipse. Unlike a solar eclipse, the Moon doesn't go into shadow but rather, will appear a reddish or copper colour. This happens because the Sun's light must first pass through the Earth's atmosphere, before reaching the Moon. Depending on the density of the atmosphere (pollution is a factor, as well as volcanic dust, which is responsible for a very dark red Moon when an eruption occurs close to an eclipse), the Moon will appear more or less red in colour.
Here's an interesting little factoid: this eclipse is the first to occur on this date since the 17th century! It will be visible after midnight Eastern Standard Time on December 21 in North and South America. The beginning of the eclipse will be visible from northern Europe just before sunrise.
Oh, and by the way, that bright object in the southern December sky at nightfall is the giant Jupiter. With clear skies, a pair of binoculars and a bit of luck, you might even spot one or more of Jupiter's more prominent satellite objects or moons; Io, Callisti, Ganymede and Europa.
Six days 'til Christmas folks!