February 2007

by Deane Morrison

We tip our hat to Saturn this month--especially on the 10th, when Earth "laps" its ringed neighbor in the race around the sun. At that moment Saturn will be like the full moon: directly opposite the sun in the sky and visible all night. The planet traverses the heavens east of the Gemini twins, between the Beehive star cluster of Cancer and the bright star Regulus of Leo.

Saturn's rings were discovered by the great Italian astronomer Galileo in 1610, but because he saw them edge-on, he couldn't tell what they were. Not until 46 years later did the Dutch astronomer Christiaan Huygens, using a much better telescope, see the rings for what they were. And the discoveries still keep coming. This year Saturn's giant moon, Titan, made headlines when researchers reported that its northern regions probably contain lakes of liquid methane, or natural gas. It's even possible that in the minus 290 F environment of Titan, methane goes through cycles of evaporation, rain and condensation, playing a role like that of water on Earth.

While you're admiring Saturn, look to the southwest and the constellation Canis Major. Its brighest star, Sirius, outshines every other star--but only because it lies a mere 8.7 light-years from Earth. It can't hold a candle to another star in Canis Major called VYCMa. This star is 500,000 times brighter and 30 to 40 times as massive as our sun, but it is 5,000 light-years away and beyond the view of the naked eye. An unstable star, it is throwing off huge streams of gas in unruly fashion, forming arcs, loops and knots of material. Recently, University of Minnesota astronomy professor Roberta Humphreys led a team that combined telescopic images to make the first 3-D images of the star and its cloudy shroud, a step that will help astronomers understand how such massive stars die.

If you're out just as the sky gets dark, you may catch elusive Mercury to the lower right of Venus, just above the sunset horizon. The tiny planet is best seen for only a few days centered on the 7th, then it pops out of sight as it heads in between Earth and the sun. Venus, however, climbs ever higher, dazzling the eye and reminding us why its name is synonymous with beauty.

Jupiter rises after midnight with the summer constellation Scorpius, just a few degrees east of its bright red star, Antares. Mars, in Sagittarius, rises later but remains a dim object in the east- southeast until dawn.

The full moon of February, called the snow moon or hunger moon by Algonquin Indians, arrives at 11:45 p.m. on the 1st. Following the new moon of the 17th, a young crescent appears below Venus on the 18th and above the planet the next evening.

Groundhog Day is a survivor from ancient Celtic times, when it was called Imbolc, or lamb's milk. It was one of four cross-quarter days falling midway between a solstice and an equinox. Cloudy weather on this day was deemed a good sign, for clouds meant warmth and rain to loosen up soils for planting. Bright sun portended cold and low humidity, which led to our modern tradition that six more weeks of winter will follow if the groundhog sees its shadow.

Late in February, star watchers lucky enough to enjoy dark skies may see the zodiacal light, a faint oval glow along the sun's path an hour or two after sunset. A waxing moon will interfere during the last week of the month, so look for it by the 18th. But you have until the 23rd to see the Gegenschein, or counterglow, unhindered by moonlight. The Gegenschein appears around midnight as a faint spot of light high in the southern sky, directly opposite the sun's position on the far side of the globe. Both the zodiacal light and the Gegenschein are caused by reflection of sunlight on meteoric dust in the plane of the solar system, stretching far beyond Earth.