| Feb 22, 2007


Night Skies

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NightSkies

The Night Skies of March 2007:A LunarEclipse andChance to view theZodiacal Light

by Leo Enright

As has been noticed by many people, sunsets are now quite noticeably later than they were a month ago. In this area at the beginning of March, sunsets 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, the end of evening astronomical twilight will move from about 7:30 p.m. to about 8:10 p.m., also a change of roughly one minute per night. This information will allow you to calculate sunset and end-of-twilight times for each day of March.

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Beginning well before the end of twilight, we can still see on every clear evening those bright and familiar stars of the distinctive winter constellations that last month were high in the southern evening sky. Now, however, they have moved well into the southwestern part of the sky, and can be seen setting at about midnight. These star patterns include the outline of Orion, the Great Hunter, with his famous 3-starred belt between his starry shoulders and knees, followed by his two faithful dogs Canis Major and Canis Minor whose eye-stars Sirius and Procyon are among the brightest in the heavens, and Gemini with the gleaming twin stars Castor and Pollux to the upper left from Orion’s shoulder, and finally the “V-shaped” Head-of-the-Bull stars that are sometimes called The Hyades. These five constellations, along with several others nearby, are the ones usually called “the Winter Constellations”, and they have more very bright stars than any other part of the whole sky. There is always some disappointment among stargazers at the prospect of such an array disappearing from their sight, but that is what will happen over the next two months, as it always does when spring approaches.

Any such disappointment is sure to be ameliorated, however, as we concentrate our views on the moon and the five bright planets over the next couple of months. It all begins right on the first evening of March with the very close conjunction of the moon and Saturn. Anyone who is outdoors on any clear evening during the whole month is likely to notice brilliant Venus well up in the west immediately after sunset. This stunningly bright planet, that is bright enough to see in full daylight, if one knows exactly where to look, will be seen slightly higher each night as the month progresses, and will increase its time of visibility from about 2 to 3 hours, if one has a perfect horizon to watch it all the way down to its setting. Just as Venus dominates the early evening western sky, so Saturn dominates the evening eastern sky, and in fact, it moves across the sky during the night and may be seen setting in the west during morning twilight. A particularly memorable sight will be the very close conjunction of the moon and Saturn on the evening of March 1st when the two objects appear to be VERY close, less than the width of a fingernail held at arm’s length. (Try it that evening. You will see that the separation is only the width of your fingernail held at arm’s length.) Owners of small telescopes may enjoy the view of Saturn this month, along with its ring system and several of its many moons. The other three bright planets are seen in the eastern morning sky. Jupiter does not rise until after midnight. This unmistakable planet, which is second in brightness only to Venus, is found to the left of the reddish star Antares, brightest star in the constellation Scorpius. Jupiter dominates the pre-dawn morning skies of March. Owners of good binoculars or small telescopes will be able to enjoy the view of this large planet and four of its many moons. Reddish Mars, well down and to the left from Jupiter, rises in the east only about 1 hours before sunrise and may be difficult to observe because of being in the glow of morning twilight – unless one uses binoculars. Mercury is also in the eastern early morning sky, rising a short while before the sun, and found down and to the left from Mar, but viewing it without binoculars will probably be impossible, and even with binoculars it will probably be seen only between March 15th and March 25th – unless one travels to the Southern Hemisphere where it will rise earlier and be much more readily visible.

Since it is now six months since the last set of eclipses, we are now into the first “eclipse season” of 2007 with two eclipses occurring this month. The first one, a Total Lunar Eclipse on the evening of Saturday March 3rd, is best seen in Europe and Africa, where it may be viewed from start to finish. In eastern North America, however, this eclipse is at least half over by the time the moon rises, and so, unless we are willing to travel, we get to see less than half of the event. Try not to miss the changing colours seen on the moon as it moves gradually through the Earth’s umbra (main dark shadow) and penumbra (lighter outer shadow). As usual sunset and Full Moonrise occur at about the same time at these latitudes, and locally that evening both events happen shortly before 6:30 p.m. EST, at which time there are only about 28 minutes remaining of the Total Phase of the eclipse. The Total Phase ends at 6:58 p.m., and the Partial Phase lasts 74 minutes, that is, from 6:58 to 8:12 p.m. EST. After the last contact of the moon with the Earth’ umbra, or central shadow (at 8:12 p.m.), it may be possible to see some slight darkening on the disk of the moon until about 8:45 or even 8:50 p.m., as the moon moves through the very tenuous penumbra or outer shadow of the Earth. The moon will not leave the Penumbra until 9:24 p.m., but that event is undetectable since the outer parts of the Penumbra are so tenuous. Try to record different colours you detect on the surface of the moon during the Total Phase. They could possible range from black to grey to orange to russet to yellow, depending the particles in the Earth’s atmosphere through which a small amount of light from the sun is refracted before entering the Umbra and being seen striking the darkened moon. In past years following major volcanic eruptions, such atmospheric particles have caused very dark eclipses for several years. At other times the Total Phase has appeared somewhat brighter. I am interested in hearing about your impressions of the event. The solar eclipse this month (on March 19th, and as always, at the time of the New Moon) is visible from parts of Asia, but from nowhere at all in North America except western Alaska.

After the eclipse event there are several moon-planet conjunctions well worth planning to see. In the middle of the nights of March 6th and 7th, the moon may be seen passing the bright star Spica, brightest star in the constellation Virgo. In the eastern morning sky, on March 11th and 12th watch the moon move past, and below, the brilliantly bright planet Jupiter. In the western evening sky on March 20th and 21st watch the slender crescent moon move upward past the planet Venus. That will be a stunningly beautiful sight! Not to be missed!

Between March 6th and March 20th, on very clear evenings beginning at the end of astronomical twilight (See first paragraph.) and lasting for a half-hour or more, The Zodiacal Light may be seen in the western sky. It is a very large “inverted glowing pyramid” caused by sunlight being reflected from billions and billions of tiny dust particles in a disk in the solar system going out as far as the orbit of Mars. No instrument required! Try to catch it this month, also!

For more information about observing the late winter sky, and events in the sky for the whole year, a book called The Beginner’s Observing Guide, is now available at Sharbot Lake Pharmacy.

Clear dark skies, and enjoy your hours of observing!

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