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Night Skies - January 5, 2006
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Night SkiesJanuary 5, 2006
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The Night Skies of January:Brilliant Venus: "Star"of evening and morning sky
by Leo Enright
As explained in an earlier column, the earliest sunset of the year, at our latitude, was on December 10. Since then, sunsets have been later each evening, but by only a few seconds each day. By the end of January, the time of sunset will go from 4:33 p.m. on New Year’s Day to 5:10 p.m. on January 31. However, the difference in day-to-day sunrise times in the chilly January mornings is not nearly so noticeable, since they range only from 7:47 a.m. on January 4, the date of the latest sunrise of the whole year in this area, to 7:31 a.m. on the last day of January.
Like December, January is the time to enjoy the late evening’s very bright star patterns in the southern sky. The huge constellation Orion the Hunter still marches across the southern sky with his hunting dogs, Canis Major and Canis Minor, following at his heels. The larger one has the brilliant star Sirius, brightest star in the whole sky, to mark its eye, and the nearby stars do seem to form the shape of a large dog. The smaller dog, slightly behind and above his companion in the sky, has the star Procyon, the sixth brightest star, to mark its location, but it has far fewer bright stars and only the poorest of a possible outline of a dog of any description. Orion himself has seven very bright stars for his distinctive outline: Betelgeuse and Bellatrix for his shoulders, Rigel and Saif for his knees and a distinctive trio of almost equal brightness to show his belt. Less brilliant, but still easily seen in rural skies, are the stars marking his head, his sword below his belt, and his raised arms, one with his club and the other bearing his shield. Below Orion’s Belt, the careful observer should take note of what astronomers call ‘the Orion Nebula’, an immense and very distant region of hydrogen gas where new stars are being born over millions of years. A small telescope will reveal several surprises within this area of the sky. Of the five bright planets, four of them can be very easily seen this month, and one of them puts on an unusual performance that reminds us of the fact that the different planets have different cycles and our own planet Earth is one of them. This month the planet Venus, by far the brightest of all the planets, is very easily seen BOTH IN THE EVENING IN THE WESTERN SKY AND IN THE MORNING IN THE EASTERN SKY. Like Mercury, which is also “inside the orbit of the Earth,” but unlike all the other planets, Venus is seen for a period of time (8 or 9 months) “to the left of the Sun” when we notice it in the evenings, and then it is seen for a period of time (8 or 9 months) “to the right of the Sun” when we notice it in the eastern morning sky. After each of those periods, particularly after the second one, there is a usually a period of days or weeks in which the planet is not seen at all because it appears very close to the sun. What happens this month is the conclusion of the first part of the Venus cycle (and the beginning of the second part). After about 8 months in our evening sky, the first of Venus’s cyclical periods is over and, on January 13, it crosses over to the other side of the Sun and will appear in the morning sky until October 23. This month, we can appreciate, in a very real way, the fact that the ancient Greeks knew this object both as Hesperus (the Evening Star) and Phosphorus (the Morning Star). In early January, we have well over an hour each evening to see Venus low in the southwestern sky, and we should begin seeing it right after the sun sets, if we have a good view of the southwestern horizon. By January 10 our time to see it each evening decreases to less than a half-hour. Without binoculars, most people will probably not see it at all between January 11 and January 17. By January 18 it has become a morning object and may be seen low in the eastern sky beginning a half-hour before sunrise. Its time of visibility in the eastern dawn increases daily until, by month’s end, it may be seen for about 2 hours before sunrise. Not only does Venus appear with great brilliancy in both parts of the sky; it also presents a very unusual phase to those who view it with a small telescope. In the first 10 days of the month, Venus appears as a very thin crescent – like the crescent moon seen in the evening sky about 2 days AFTER New Moon. In the last 12 days of the month it appears “reversed” -- like the slim “old” Crescent Moon seen in the morning sky about 2 days BEFORE New Moon.
Let us not forget the other planets. Reddish Mars is easily found high in the southwestern evening sky and to the right of the famous Pleiades star cluster. Careful observers will easily notice two things about it this month: its brightness fades notably as the distance between Earth and Mars increases, and it appears to move eastward in the sky and toward the Pleiades by more than 10 degrees (the width of your fist held up at arm’s length). Saturn rises in the east after twilight begins and dominates that part of the sky in the first half of the night. Bright Jupiter is seen in the morning sky, rising in the east about 3:00 a.m. in early January and earlier each morning until, by late January, it may be seen as early as 1:00 a.m. Careful observers should try to note two things about Jupiter: it increases slightly in brightness over the month and its movement may be noted in relation to a background star that appears very close to it. That star is the brightest star in the constellation Libra, and a small telescope or binoculars can show that the star is actually a “double star.”
Several lunar conjunctions are well worth viewing this month. On the evening of January 8, the waxing gibbous Moon is about 2 degrees to the left of Mars. During the night of January 14, the Full Moon is close to Saturn and those who check the pair of them during the night will notice that the Moon’s orbit seems to be carrying it closer to the planet hour-by-hour until, by moonset, it is twice as close to Saturn as it was in the early evening. In the morning sky on January 23, the waning crescent moon will be to the lower right of Jupiter, and on January 25 very close to the bright red star Antares, the brightest star in the constellation Scorpius. At dawn on the 27th the low eastern sky will present a very thin Crescent Moon well to the right of brilliant Venus. Try to see as many of these conjunctions as possible. They give us a set of spectacular pictures of bright heavenly objects, and, over the course of a month, a fundamental appreciation for the orbital speed of the Moon as it travels around the Earth.
Much more information about observing winter constellations and other objects of the night sky is available in the latest edition of the book, The Beginner’s Observing Guide, now available at Sharbot Lake Pharmacy. Very good wishes for 2006, and remember to enjoy the beauty of the winter sky!