Skywatchers’ Guide for March 2010
HIGHLIGHTS: Mars is bright, large and up for most of the night at the beginning of the month. Ringed Saturn becomes more prominent in our March evening sky and is at opposition on March 21. Also, the stars of the winter sky still shine high and bright early on March evenings, making this month one of the best for evening stargazing, especially from the Desert Southwest.
PLANETS
 This chart shows Mars, the Moon and the winter sky as seen on March 24 at 8:15 p.m. Mountain Standard Time (MST), facing southwest.  This chart shows Saturn, the Moon and the eastern sky as seen on March 28 at 9:15 p.m. MST (facing east).  This chart shows Venus, Mercury and the western evening twilight sky on March 28 at 7:30 p.m. MST |
The planet Mars is still bright but is decreasing in brightness and apparent size this month, as it was at opposition on January 29. Mars rises well before sunset and is up almost all night long. As it is moving higher in the eastern evening sky, Mars will set earlier in the western morning predawn sky. Mars begins the month retrograde (moving backward) in Cancer the Crab, but turns back to prograde (normal eastward motion) on March 11. Also, look for the 9 day old waxing gibbous Moon nearest Mars in our sky this month in the east on Wednesday evening, March 24.
Venus, emerging out of the glare of the Sun, is a bright evening ’star’ for about an hour after sunset. It’ll be visible low above the western horizon, starting 20-30 minutes after sunset. The razor thin waxing crescent Moon (only one day old) will be nearest to Venus on March 16. Mercury, reaching superior conjunction (directly behind the Sun) on March 14, also becomes an evening ’star’ just below Venus for the last few days of the month. Jupiter, having passed conjunction with the Sun on February 28, will become barely visible to the naked eye very low (only 2 degrees) above the eastern dawn horizon the last few days of March, starting around 40-45 minutes before sunrise.
Ringed Saturn reaches opposition on March 21, and will be visible in our evening sky nearly all night long. It rises by 1.75 hours after sunset on March 1, but rises by 1.25 hours before sunset by the end of the month. Saturn is found below the constellation Leo the Lion in Virgo, the Virgin. Also look for the 15 day old waning gibbous moon to appear below and closest to Saturn in our sky on Monday evening, March 1 (into Tuesday morning, March 2). The full moon will pass Saturn again on March 29.
Visitors to Flandrau’s 16-inch telescope should note that Saturn should become visible above campus buildings by 9 p.m. on March 1, by 8 p.m. on March 15, and by 7 p.m. on March 31 (Wed-Saturday, weather permitting, during public hours). Other celestial objects will be shown in the telescope, weather permitting. Although Flandrau’s main exhibit hall and planetarium are now closed to general public programs due to state budget cuts, groups of all kinds can arrange for planetarium shows and Mineral Museum field trips. The Mineral Museum is normally open Wednesday through Saturdays to the public from 9:00 a.m. to 5:00 p.m. (and by appointment). The Flandrau Observatory remains open for viewing during public hours from 7-10 p.m., weather permitting, Wednesday through Saturday nights (excluding select holidays).
Finally, remember that in spotting planets there is a general rule: “stars twinkle, planets don’t”. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere. However when looking at Mercury this month, note that it may appear to twinkle somewhat; however, this twinkling is of a slower nature than that of the bright stars.
Zodiacal Light Visible
March is an excellent month, and Arizona is a superb place, to look at the Zodiacal Light in the western evening sky, starting 75 minutes after sunset. The Zodiacal Light is sunlight reflecting off of meteoritic dust in our solar system. Because this dust lies along the plane of the solar system, we see its faint glow as a cone of light along the constellations of the Zodiac. Often confused with light pollution or twilight, the Zodiacal Light must be seen on clear moonless nights, in dark locations far away from city lights. In March look for the faint colorless cone shaped glow of the Zodiacal Light to reach high up from the western horizon towards the Pleiades, or ‘Seven Sisters’ star cluster.
Vernal or Spring Equinox occurs on Saturday, March 20
On Saturday, March 20, at 10:33 a.m. MST (Mountain Standard or Tucson time), the sun crosses the celestial equator on its way north, marking the spring or Vernal Equinox. The sun on the equinox stands directly overhead from the equator at noon. The name Vernal Equinox means “green time of equal night and day”. Night and day on the equinox take essentially equal amounts of time for most parts of the world.
MARCH EVENING STARS
 The March western evening sky at around 90 minutes after sunset as seen on moonless nights far away from city lights in the southwestern United States. Note: This sky chart is most useful throughout the southern United States and northern Mexico.  The Big and Little Dippers and the northern sky at 8:30 p.m. in middle March. ‘Arc to Arcturus’ off the handle of the Big Dipper. This sky chart is useful throughout the United States, southern Canada and northern Mexico.  The northeastern sky in March at around 10:45 p.m. in early March, at 9:45 p.m. in mid-March and at 8:45 p.m. in late March as seen from the southern U.S. ‘Arc to Arcturus’ and then ’speed on to Spica’ off the handle of the Big Dipper. |
The bright stars of winter still dominate the evening March sky, but shift to the western half of the sky early. Look for Orion, the Hunter, and his shimmering belt of “three stars in a row” to find other sights in the winter sky. Orange Betelgeuse, the shoulder of Orion the Hunter, shines upper left of Orion’s 3 glittering belt stars and blue white Rigel shines below. The Gemini Twins, the bright stars Castor and slightly brighter Pollux, twinkle left of Orion. Castor will be above Pollux. Take Orion’s belt and point down and left to Sirius, the brightest star in all the heavens. Sirius is the nose of the Greater Dog, Canis Major, a companion to Orion in the heavens. Later in the evening, Orion and his winter companions will set in the western sky. Orion’s belt will then point left to Sirius when in the western sky. Betelgeuse at that time can be found directly above Orion’s belt.
The Big Dipper is easy to find this March (and every March) in the northeast evening sky. Look for the Big Dipper high in the northeast 1-2 hours after sunset. Take the two ends stars off of the bowl (the Pointer stars Dubhe and Merak) and point to Polaris, the North or Pole Star. Polaris is a star of ordinary brightness, and marks the end of the handle of the Little Dipper. Polaris is a direct indicator of latitude and so is always found the number of degrees above the northern horizon equal to an observer’s latitude. In Tucson look for Polaris about 30 degrees (or 3 fists) above the northern horizon. Polaris stays put in the sky, so to the eye it doesn’t appear to move. This is because Earth’s axis is pointed toward Polaris in space.
The Big Dipper is an amazing signpost in the heavens, useful in finding many notable sights in the sky. The two stars forming the outside end of the Big Dipper’s bowl — the part opposite from the handle — are called “the Pointers.” A line drawn through them points quite near the North Star, Polaris. Polaris closely marks the north celestial pole, and hence appears not to move in the sky to the unaided eye. Polaris is also the end of the handle of the Little Dipper, whose other name is Ursa Minor, the Little Bear. Continue straight down from Polaris to the horizon to find true north. Polaris always remains at almost exactly the same point over the northern hemisphere landscape, day and night, and is always there to mark almost exactly due north. Polaris is not a very bright star, but it is in a dim part of the sky where there is nothing else to confuse it with. Come back to the Big Dipper and follow the curve of the Dipper’s handle back across the sky by about two handle-lengths and you’ll see the brightest star of spring, the bright yellow-white star Arcturus. Continue down from Arcturus to “spike” or speed onto the blue star of spring, Spica.
MOON PHASES
The March last quarter Moon will occur on Sunday morning, March 7. The March New Moon occurs on the afternoon of Monday, March 15. The March first quarter Moon occurs on Tuesday morning, March 23. The March 2010 Full ‘Worm’ Moon will occur on Monday night, March 29.
Note: Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
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