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The Sky This Week, 2010 March 23 - 30

Planets gather in the night, and a special Full Moon.
mars12_100320_0259_01small.jpg sat12_100320_0241_01small.jpg
MARS, 2010 MAR 20, 02:59 UT SATURN, 2010 MAR 20, 02:41 UT
Images made with the USNO's 12-inch (30.5-cm) f/15
Clark/Saegmüller refractor

The Moon waxes in the evening sky this week, brightening the budding spring landscape as she approaches the Full phase.  Full Moon occurs on the 29th at 10:25 pm Eastern Daylight Time.  As the first Full Moon to follow the vernal equinox, this one fixes the dates of two religious observances, Passover and Easter.  This Full Moon is popularly known as the Sap Moon, Crow Moon, Lenten Moon, or Paschal Moon.  Look for Luna near ruddy mars on the evenings of the 24th and 25th.  On the 26th the Moon lies about six degrees southwest of the star Regulus, and on the 28th and 29th she passes by the golden glimmer of Saturn.  On the evening of the 30th she may be found just three degrees south of the bright blue-tinted star Spica.

As Luna brightens the sky she washes out the fainter stars among the rising springtime constellations.  Fortunately the early evening sky still hosts the bright stars of the Great Winter Circle, which surround the central figure of Orion.  These stars are quite visible as evening twilight fades and they slowly glide into the southwestern sky.  However, as the Moon waxes and the night darkens, the fainter stars of the spring constellations begin to get lost in the glare, and only the few bright stars of the season prevail.  If you look toward the south and east when the Moon is bright and it’s late at night, three fairly prominent stars and a planet stand out.  Highest up is the star Regulus, the heart of Leo, the Lion.  Over in the eastern sky a bright, slightly rose-tinted star is the sole real beacon of spring, the star Arcturus.  Finally, low in the southeast, you’ll find the bright star Spica.  The planet, which lies between Spica and Regulus, is distant Saturn.

The early evening finds brilliant Venus climbing slightly higher each night in the west after sunset.  Venus is very hard to miss now, although she is often mistaken for an airplane in an airport landing pattern.  She is brighter than any other evening object except the Moon, and by the end of the week she sets at the end of evening twilight.  She is joined by week’s end by the fainter planet Mercury, who seems to leap up from the horizon on the way to the year’s best evening apparition for this fleet world.  On the 30th the duo are separated by about three degrees, with Mercury below and to the right of Venus.  With a clear sky and low horizon you shouldn’t have any trouble spotting Mercury in the middle of evening twilight at this time.

Mars has now resumed “direct west-to-east motion against the background stars.  The red planet is slowly gathering momentum and beginning to widen the gap between himself and the Gemini twins.  He now transits the meridian at the end of evening twilight and grows a tad dimmer with each passing evening.  Mars will linger in the evening sky throughout the spring and summer months as he wends his way eastward through the stars of Cancer, Leo, and Virgo.  By the end of July he will be part of a planetary “traffic jam” in the southwestern sky along with Mercury, Venus, and Saturn.

Saturn is now visible in the sky all night long, having reached opposition on the 21st.  This is the best time to observe the ringed planet through a backyard telescope since he is being directly lit by the Sun with virtually no phase effects.  This tends to make his smaller moons brighten by half a magnitude or so for about a week before and after the date of opposition.  This effect can be very dramatic on the rings when they are wide open, but this year, with their almost edge-on appearance, the effect is much more subtle.  Still, Saturn’s disc is a treat to observe after squinting at the shrinking dot of Mars, and the rings and scattered moons are just more icing on the cake.

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