| Mar 03, 2005

Feature article, March 3, 2005

Feature article March 3, 2005

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Chance to see Mercury and a Lunar Occultation

As most people have started to notice, sunsets are considerably later than they were a month ago. In this area, at the beginning of March, sunset is just a few minutes before 6:00 p.m. EST, and by the end of the month it will be about 6:30 p.m., occurring about one minute later each evening. Over the month of March, the end of evening astronomical twilight moves from about 7:30 p.m. to about 8:10 p.m., also a change of about one minute per night. This information will allow you to calculate sunset and end-of-twilight times for each day of March.


Beginning even before the end of twilight we can easily see that the bright and familiar stars of the winter constellations that last month were high in the southern sky have now moved well into the southwestern part of the sky, and will be setting about midnight. These constellations include Orion, the Great Hunter, with his distinctive 3-starred Belt midway between his starry shoulders and knees, followed by his Great Dogs, Canis Major and Canis Minor, whose eye-stars Sirius and Procyon are among the brightest in the whole sky, and following in the distance behind his upraised arm, the twin stars of Gemini, Castor and Pollux. Preceding Orion down into the western sky is the V-shaped head of Taurus, the Bull, a large pattern of stars known as the Hyades Cluster, with the smaller Pleiades Cluster (known in Japan as the Subaru) to its right and apparently riding on the back of the great bovine creature. These five constellations, along with several others nearby, have more bright stars than are found in any other part of the heavens. Is it any wonder that there is some disappointment at seeing such a splendid array disappear from the evening sky, for that is what will happen over the next two months?

Any such disappointment is sure to be soon forgotten, however, as we concentrate on our views of the sprawling springtime constellations, and the bright planets that are spread across the sky this month. To begin with the inferior planets (the two whose orbits are inside our Earths orbit), we can say that this is the month of Mercury and not the month of Venus. Although we have had splendid views of brilliant Venus in the morning sky over the past eight months (and for me, up to the time of my most recent sightings on January 25th, 26th, and 27th), Venus is now at the part of its orbit which is on the far side of the sun, and it will not be easily seen until May when it will appear on the other side of the sun and become visible in the evening sky. Mercury will give us a chance to experience what we may miss in not seeing Venus, because Mercury, which is rarely seen by most people, will have its best evening appearance of the whole year, and will be very easy to spot, if one has clear skies and plans to observe at the right time and place. Since it will be low in the western sky, choose a location with a very good view of the western horizon. Begin looking about 45 minutes after sunset (See first paragraph.), and look due west for the next 45 minutes or more. You should see what appears to be a bright star, appearing slightly higher above the horizon on each of the first 12 days of the month, and then after that appearing slightly lower and fainter each evening until about March 20th when it will become very difficult to see in the evening twilight. Since so few people are certain of ever having seen this planet, all are urged to follow these guidelines for some rare, but easy, sightings of Mercury this month. Saturn is extremely high in the sky in the early evening, and still in the constellation Gemini where it has been for the past year. Just as very careful observers have been able to notice its apparent movement away from the stars Castor and Pollux over the past two months, so they may begin to notice on March 21 or thereabouts, that its apparent motion is beginning to take it slowly back toward the star Pollux, which is the lower of Geminis twin stars. This observed change in its apparent position is actually the result of the combination of the orbital motions of both Saturn and Earth. People who have a small telescope are bound to be rewarded with interesting views of Saturns rings and some of its many moons, including Titan, the moon which has revealed such interesting features in the past two months, following the Cassini-Huygens spacecraft mission to this largest moon of Saturn. On March 1st, the planet Jupiter rises in the east about an hour after the end of twilight, but it may be seen rising earlier each evening until by months end it can be spotted low in the east shortly after sunset. This largest planet of our solar system, is also the brightest planet currently seen, since Venus is not visible this month. Jupiter dominates the eastern half of the sky before midnight and the western half after midnight. It is down in the western sky and about to set at about the time of sunrise. Those with a small telescope should direct it toward this magnificent object in order to see the dance of its four brightest moons around the planet, but they should wait until it is high enough in the eastern sky to avoid the low-lying haze and atmospheric turbulence; then enjoy the fascinating view of a planet with numerous cloud bands and the four bright moons which Galileo saw in his first telescopic view 395 years ago. Reddish Mars will be the faintest of the four bright planets to be seen this month. (I have been watching it over the past two months as it passed by the star Antares with which it has been compared for centuries.) It rises in the southeast at about 4:00 a.m, in early March, and a little earlier each morning until it is seen at 3:00 a.m. by March 31st. Mars now appears to the left of the stars of Sagittarius which presents the outline of teapot. Careful observers will notice that it slowly increases in brightness over the month, a hint of its much brighter appearance later this year.

An event anticipated by many skywatchers will be the lunar occultation of the bright red star Antares just slightly after 6:00 a.m., that is, during twilight, on Thursday March 3rd. Set the alarm so as not to miss the chance to see a fairly rare event: the Last Quarter Moon coming close to and then occulting, or hiding, this star. Binoculars or a small telescope will allow you to precisely time the event. On the mornings of March 5th and 6th, you may see an old crescent moon near Mars about an hour before sunrise. In the evening sky, on March 11th and 12th, the crescent moon is near Mercury, and on March 18th and 19 the gibbous moon is near Castor and Pollux and Saturn. On March 25th and 26th the Full Moon glides past brilliant Jupiter.

More information about these and other objects to observe throughout the year is available in the book, The Beginners Observing Guide, now available at The Valley Book Shop in Perth and at Sharbot Lake Pharmacy. Clear skies, and successful observing!

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