Little Bear runs with meteors just in time for the week's holiday revels, as stargazers enjoy the moon going caroling with our nearest and dearest neighbors, Venus and Mars.
Little Bear shower. The night of Monday, December 22, will see the Ursid meteor shower, which peaks with a modest 5 to 10 shooting stars per hour.
Each and every streak of light you see in the shower comes courtesy of sand-grain-size cosmic dust, particles shed by the passage of comet Tuttle, discovered in 1790, on its 14-year circuit around the sun.
Meteor showers owe their names to the constellations from which they seem to radiate. That explains the Ursids, which seem to trace their path from Ursa Minor, the Little Bear, in the northeastern evening sky. The best views arise after the moon sets around midnight, in dark skies away from city lights. (To read about the 1833 origins of meteor shower names, click here.)
Moon meets Venus. After sunset on Tuesday, December 23, look for a razor-thin crescent moon perched above a brilliant Venus.
The cosmic duo will be quite an observing challenge for sky-watchers in North America as all the action happens close to the glare of sunset.
Moon meets Mars. As dusk turns to twilight on Christmas Eve, December 24, a ruddy Mars shines on beside the moon. Look for the faint, orange hue of the planet about 6 degrees left of the moon, which is equal to the width of your three middle fingers held at arm's length.
It's amazing to think that while the two look close together in the sky, the moon is actually 1.21 light-seconds away, but Mars is so distant that its light takes just over 16 minutes to travel to us on Earth.
Lunar X. After darkness falls on Sunday, December 28, the moon will reach its first quarter phase. This represents the best time to catch sight of a unique lunar feature, one where X marks the spot.
On the moon at this time, a weird topographical formation will appear for only about four hours—a letter X, visible with the smallest telescope or even with steadily held binoculars. While it does look artificial, this conspicuous feature, called the Werner X, is actually formed by the walls of three craters clustered together.
The optical illusion appears when sunlight hits the rims of the craters at just the right angle while the crater floors are in total darkness. Not many people have seen it because it's visible for only a few hours each month. Now is your chance.
Start your hunt for the lunar Werner X about a third of the way up from the heavily cratered, southern limb of the moon, along the terminator line (where light and darkness meet). You'll find a good chart with observational details in this article.