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The Night Sky of March

Dr. Wayne Wooten
Professor of Astronomy

For March 2012, the Moon will be first quarter on March first, rising about noon and high overhead at dusk. The full moon, the Grass Moon, will pass nine degrees south of bright Mars on March 7th; Mars came to opposition on March 3rd, so will be a bright red object near the moon and get a lot of attention that evening. We will spring forward to CDT on Sunday morning, March 11th, the same morning the waning crescent moon passes six degrees south of Saturn in the dawn sky. The moon is last quarter on March 15th.

The Vernal Equinox has spring beginning on March 20th at 12:13 AM CDT, as the sun crossed the equator heading north. The moon is new on March 22nd. It passes three degrees north of Jupiter in SW on March 25th, then passes about two degrees north of brighter Venus on March 26th. This would be a great time to use the crescent moon in the afternoon sky to help you find Venus in broad daylight. About 5 PM on March 26th, look for Venus to the lower right of the crescent moon. The moon returns to first quarter phase on March 30th. This complete phase cycle is called the synodic month, and takes about 29.5 days; it is the basis of our modern month in the early lunar calendars of the Romans, Jews, and Muslims.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. For a detailed map of northern hemisphere skies, about March 1st visit the website and download the map for the new month; it will have a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map.

It is a great month to be observing the planets. Mercury makes a brief appearance in the evening sky as the month begins in the SW, reaching greatest eastern elongation about March 5th, but then retrogrades quickly back between the earth and Sun by midmonth. But brilliant Venus finally overtakes much slower moving and more distant Jupiter in the western sky on March 13th, with Venus passing three degrees north of Jupiter in the evening twilight. Venus is overtaking Earth as well, and reaches greatest eastern elongation, when she will appear exactly half lit to earth based telescopes, on March 27th. But by then, Jupiter will be getting lower in the SW each evening, to disappear in the Sunís glare in April.

But the real planetary treat is in the east, as we overtake Mars and it comes to opposition, rising in the east at sunset in Leo on March 3rd. At that closest approach to earth, Mars shines bright red at mag. -1.4, almost as bright as Sirius the brightest star, in the SW now. Its disk is 14" of arc across, and scopes 6" or larger at high magnification may spot its north polar cap, shrinking in the martain spring, as well as some dark markings in its red deserts. Marsís orbit is elliptical, and we were unusually close to Mars back in August 2003, when Mars was almost twice as close and large as it will get this March, but still worth checking out with big scopes.

Remember the nice Full Moon grouping with it on March 7-8. Finally, Saturn is still in the morning sky in Virgo, but will come to opposition in the evening sky on April 15th, so those who stay up late can observe it rising in the east about 9 PM in mid March, and about 8 PM at the end of the month. In fact, by March 30th, you can spot Jupiter low in the SW, Venus shining brightly about 15 degrees above it, then Mars well up in the NE in Leo, and Saturn rising in the east around 8:30 PM. Only Mercury, now moving into the dawn sky, will be missing from our March Planetary Parade.

The constellation Cassiopeia makes a striking W in the NW. South of Cassiopeia is Andromedaís hero, Perseus. Between him and Cassiopeia is the fine Double Cluster, faintly visible with the naked eye and two fine binocular objects in the same field. Perseus contains the famed eclipsing binary star Algol, where the Arabs imagined the eye of the gorgon Medusa would lie. It fades to a third its normal brightness for six out of every 70 hours, as a larger but cooler orange giant covers about 80% of the smaller but hotter and thus brighter companion as seen from Earth. At Perseusí feet for the famed Pleiades cluster; they lie about 400 light years distant, and over 250 stars are members of this fine group. East of the seven sisters is the V of stars marking the face of Taurus the Bull, with bright orange Aldebaran as his eye. The V of stars is the Hyades cluster, older than the blue Pleiades, but about half their distance.

Yellow Capella, a giant star the same temperature and color as our much smaller Sun, dominates the overhead sky in the northwest. It is part of the pentagon on stars making up Auriga, the Charioteer (think Ben Hur). Several nice binocular Messier open clusters are found in the winter milky way here. East of Auriga, the twins, Castor and Pollux highlight the Gemini; it is directly above us as darkness falls in early March. The star names are associated with Jason and the Golden Fleece legend, for they were the first two Argonauts to sign up on his crew of adventurers.

South of Gemini, Orion is the most familiar winter constellation, dominating the southern sky at dusk. The reddish supergiant Betelguese marks his eastern shoulder, while blue-white supergiant Rigel stands opposite on his west knee. Just south of the belt, hanging like a sword downward, is M-42, the Great Nebula of Orion, an outstanding binocular and telescopic stellar nursery. The bright diamond of four stars that light it up are the trapezium cluster, one of the finest sights in a telescope.

In the east are the hunterís two faithful companions, Canis major and minor. Procyon is the bright star in the little dog, and rises minutes before Sirius, the brightest star in the sky. Sirius dominates the SE sky as darkness falls. At 8 light years distance, Sirius is the closest star we can easily see with the naked eye from West Florida. Compare its brightness about March 3rd to Mars, coming to opposition; does Mars ever appear as bright to you as Sirius does? When Mars was at opposition in August 2003, it was much closer, and was for a few weeks about five times brighter than Sirius, almost as bright as Jupiter appears!

When Sirius is highest, along our southern horizon look for the second brightest star, Canopus, getting just above the horizon and sparkling like an exquisite diamond as the turbulent winter air twists and turns this shaft of starlight, after a trip of about 200 years!

To the northeast, look for the bowl of the Big Dipper rising, with the top two stars, the pointers, giving you a line to find Polaris, the Pole Star. Look for Mizar-Alcor, a nice naked eye double star, in the bend of the big dipperís handle, rising by 7 PM at the start of March. If you take the pointers of the Big Dipperís bowl to the south, you are guided instead to the head of Leo the Lion rising in the east, looking much like the profile of the famed Sphinx. The bright star at the Lionís heart is Regulus, the "regal star".

If you follow the handle of the Big Dipper to the south, by 9 PM you will be able to "arc to Arcturus", the brightest star of Spring and distinctly orange in color. It color is an indication of its uniqueness. It large speed and direction through the Milky Way suggests it was not formed with our Galaxy, but is a recent capture from the Sagittarius Dwarf Galaxy, a smaller satellite galaxy now being assimilated by our huge spiral galaxy. Many of its lost stars, like Arcturus, follow a band across the sky at about a 70 degree angle to our galactic plane. Arcturus is at the tail of kite shaped Bootes, the celestial bear driver chasing the two bears from his flocks.

By 9 PM, many more galaxies will be following as the Virgo Supercluster, just above Saturn now, rises in the east. This huge cluster of over a thousand galaxies is centered about 60 million light years away. The brightest star of Virgo, Spica, lies just east of the center of the cluster, and its rise just after sunset marks the time of year for spring planting in folklore. Time to get your peas in the groundÖ.

March goes out like a lamb, not just from Easter tradition, but because Aries the Ram is setting in the west by the end of March. Many of our sayings and traditions have astronomical origins.

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