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The Sky This Week, 2014 February 4 - 11

A great week for the urban skywatcher!
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 The Moon and the planet Mercury, 2014 FEB 1, 23:22 UT


The Moon courses her way through the evening sky this week, seemingly vaulting up from the horizon to join the stars of the Great Winter Circle. First Quarter occurs on the 6th at 2:22 pm Eastern Standard Time. Look for the Moon near the Pleiades star cluster and the bright star Aldebaran on the evening of the 7th. On the 10th she may be found just over five degrees south of bright Jupiter. If you look carefully that evening you should see the second-magnitude star Alhena just a degree south of Luna’s southern limb.

This should be a banner week for the urban skywatcher. Despite the scattered light from thousands of poorly-engineered streetlamps, billboards, and other assorted sources of light pollution, the Moon, Jupiter, and the bright stars of the Great Winter Circle give you plenty of targets to focus on over the next several nights. If I had to choose the best week of the entire year to observe the Moon, this would be it. Luna waxes through the First Quarter phase as she moves through high northern declinations, allowing us to look at her through a minimal amount of terrestrial atmospheric turbulence. The sunrise terminator steadily advances across some of the most interesting formations of the lunar landscape. Early in the week the scene is dominated by many of the vast lava plains that form the so-called lunar "seas". As Luna reaches the First Quarter phase the view begins to shift toward more rugged terrain dominated by enormous impact craters. By the end of the week it once again reveals more subtle landforms as it moves across the vast Oceanus Procellarum, a huge relatively flat lava plain sprinkled with more solitary craters. These flatter areas were formed about 3 to 3.5 billion years ago, yet they represent some of the youngest terrain on the Moon. The crater-packed southern highlands have changed little since the early formation of the Moon, and among the samples returned from this region by the astronauts of Apollo 16 was the "Genesis Rock", a sample of primordial crust thought to be some 4.6 billion years old! If you marvel at the detail visible through a telescope, try to keep in mind the scale of the surface you’re examining. Even in our 12-inch telescope, the smallest features visible under ideal conditions are craters comparable in size to Meteor Crater in Arizona!

You can still catch the elusive planet Mercury early in the week. The fleet planet may be seen in the west-southwestern sky shortly after sunset about 10 degrees above the horizon. Mercury will begin a rapid plunge toward the Sun by the evening of the 8th, and he’ll fade rapidly as he does so. Try to catch him in binoculars before he goes; however, if you miss him, he’ll be back for another good evening show in the latter half of May.

Jupiter now crosses the meridian just before 10:00 pm, so you have the entire evening to observe him at a high altitude in the sky. It should be especially interesting to look at him on the evening of the 10th, when our own Moon will be just a few degrees away. Even though Jupiter presents the largest apparent disc of any planet except Venus, his size compares to an average-sized crater on the surface of the Moon. The difference, of course, is that the Moon is just 384,000 kilometers (239,000 miles) away while Jupiter is 660 million kilometers (410 million miles) distant from Earth. To put this in some sort of perspective, a good six-inch telescope will show the tiny discs of Jupiter’s four Galilean moons. On the night of the 10th the moons Io and Europa will be closest to their hulking master. These two moons are comparable in size to our Moon and subtend discs just over one arcsecond in apparent diameter. Our Moon will be just under 1800 seconds of apparent diameter!

Ruddy Mars now rises just before 11:00 pm, so the best time to look for him is still in the pre-dawn hours. The red planet is now slowing his eastward progress among the stars of the constellation Virgo as he prepares for opposition in early April. He’s currently within five degrees of Virgo’s brightest star Spica, and he’ll stay close to the star for the next several weeks. Modest telescopes can now reveal considerable detail on his distant dusty surface for those observers willing to wait for moments of steady air in our atmosphere.

Saturn is just east of the meridian at 6:00 am EST. His golden glow may be spotted between the rising stars of Scorpius and the scattered stars of Libra. Despite his southerly declination he is a wonderful sight in almost any telescope thanks to the spectacular set of rings that surround his gaseous disc. The rings are tipped just over 20 degrees to our line of sight, so even in binoculars the planet has an unusual oval appearance.

You should be able to easily spot the dazzling planet Venus low in the southeast as morning twilight gathers. Venus reaches her greatest brilliancy for the year this week, so she should be visible despite the glow of the rising Sun. Venus will remain a fixture in the morning twilight sky until late October.