Nightskies_09-04

Jeff Green | Jan 27, 2009

by Leo Enright

In the month of February, skywatchers have the chance to continue observing the distinctive winter constellations and their numerous brilliant stars during the early part of the night and later in the night to preview the spring constellations emerging in the eastern sky. In addition, this month brings the opportunity of seeing all of the bright planets, but at widely different times of the night.

At the end of evening twilight, the distinct outline of Orion, the Great Hunter, emerges in the southern sky, outlined by seven brilliant beacons: Betelgeuse and Bellatrix marking his shoulders, Saif and Rigel outlining his knees, and the trio of Alnilam, Alnitak, and Mintaka indicating his belt. In addition, a huge circle of six stars, often called The Winter Sextet, surrounds the Great Hunter – Sirius and Procyon to his lower left showing the presence of his two faithful dogs, whose surrounding stars outline Canis Major and Canis Minor; Castor and Pollux, the Gemini stars of the Heavenly Twins seen above the hunter’s right shoulder; Capella, sometimes known as ‘the Goat Star’ surrounded by her ‘kid-stars’, located well above the hunter’s head; and the reddish star Aldebaran among the cluster of stars that show the Head of the Bull called Taurus located above the stars marking the shield held on the hunter’s left arm. For people who consider Castor and Pollux a single object in the great circle, the “circle of six” is completed by the star Rigel which marks one of Orion’s knees; others may say the “circle of six” is completed without Rigel. Of the 14 stars just mentioned, all are among the brightest seen in the sky at any time of the year. Sirius, in fact, is the brightest in the whole sky, and all the others in the Great Circle are in the sky’s “top 25". On crisp, clear February nights be sure to enjoy this stunning display of heavenly brilliance.

This month all five of the bright planets may be seen, but at very different times of the night – one of them throughout evening twilight and a bit thereafter; one of them before midnight and for the rest of the night; and finally three of them for a short period of time in the morning, in the hour before sunrise. Venus, which is seen in the southwestern sky immediately after sunset, is at its most brilliant showing of the whole year. It sets over three hours after the sun sets. No, Venus is not a UFO or lights of an aircraft directed at you! Indeed, Venus is now bright enough to see with the unaided eye during daylight hours, that is, well before sunset. It is now, also, bright enough to cast a shadow after the sky has become dark, and I suggest trying to see your shadow from it alone on a clear night between February 15 and 25 when moonlight will not interfere. On the evening of February 27, if the sky is clear, we will have a chance to witness one of the truly spectacular sights of the year 2009 when the two brightest of the night sky’s luminaries, the moon and Venus, are in very close conjunction as seen from Earth. That evening, the separation between the lunar crescent and the planet will appear only slightly more than the width of a fingernail held at arm’s length. Do not miss this spectacle! Better yet: share it with friends or family. Better yet, also, if your schedule allows it, find the crescent moon in mid-afternoon in the southern sky and use it to guide you to the planet Venus just to its right and slightly upward, and thereby prove to yourself that Venus can be seen in the daylight hours. (Binoculars should not be necessary to find the moon in the afternoon, but if they are used, be very careful with them; NEVER point them toward the sun.) Mark down that date: February 27!

The planet Saturn, which is seen among the stars of the constellation Leo the Lion, rises in early February before 9PM, and a little earlier each evening until, by the end of the month, it may be seen rising before 7PM. It may be seen moving across the sky during the entire night. Owners of small telescopes always enjoy watching Saturn with its rings and several of its many moons, but this month they should remember that the rings will appear very thin because we have just passed one of the two periods of time in Saturn’s 29-year orbit around the sun when the rings are exactly in line with planet Earth, and when that happens, the rings appear very thin indeed, and for a time even seem to disappear. In a telescope, Saturn’s largest and brightest moon, called Titan, is very easy to see close to the planet, and its position should be noted and drawn, so that its changed position in its orbit around Saturn can be noted the next time it is observed. Titan orbits Saturn once in about 16 days, a little more than half the time it takes our Moon to orbit our planet.

The remaining bright planets are more challenging to see this month. Mercury, Mars, and Jupiter may be seen in February low in the eastern sky in the hour BEFORE sunrise. This means that a clear, unclouded sky is required in the east, and a clear, unobstructed view right down to the horizon. Binoculars will be required to see Mars, the faintest of the trio. In early February Mars appears on the left and Mercury on the right, but Jupiter is absent until about February 15, when it appears very close to Mars. Jupiter then appears to move to the right and is very close to Mercury on the morning of February 23. This dance of the three planets low in the eastern morning sky will become an even more spectacular sight on three mornings – February 21, 22 and 23 – when the slim Crescent Moon will join in the dance. On the 21st, the moon will be well to their right; on the 22nd, it will be just slightly to their right, and on the 23rd, the extremely thin crescent will be to the left of all of them, but very close to the horizon if viewed just 30 minutes before the sun rises. (Again remember, if binoculars are used, put them away before sunrise because one must NEVER use them to look at the sun.) On the morning of the 24th, the trio will appear closest of all, and they will fit in the field of almost any normal pair of binoculars; it’s a rare event when three planets can be seen without moving your binoculars at all. Although the weather may not cooperate on all of these mornings, try to catch this rare spectacle at a suitable location on at least one or two of the dates given.

Although several important lunar-planetary conjunctions have just been mentioned, there are also two other interesting lunar conjunctions. On the evening and night of February 3, the moon moves in front of, and hides, some of the stars in the very famous star cluster called ‘The Pleiades’ or ‘Seven Sisters’. Use ordinary binoculars to see those stars disappear at the left edge of the moon and later pop into view again at the right edge as the moon move past them. Also, on the night of February 11, the moon appears fairly close to the planet Saturn in the constellation Leo the Lion.