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Sky Report -April 2009

Spring Full Moon Triggers Easter, Venus & Mars at Dawn and Mercury Visits 7 Sisters

April opens with a half full moon, the best moon shape to see the craters with binoculars (held steadily). The moon’s craters are rather shallow, produced by the impact of huge space rocks; most of  these collisions occurred  in the early days of the solar system  when there was much debris floating through space. Most craters have the same color as their surroundings. What makes the craters stand out is lunar sunrise or sunset when the sun’s slanting rays catch the crater rims while the crater bottoms are in darkness. The evening half full moon has its lunar sunrise line along the straighter (left) edge of the lighted moon. There the larger craters, dozens of miles across can be glimpsed with  binoculars held steadily. The full moon on April 9th shows little shadows, and then the moon’s grey lava fields are the most prominent features seen with binoculars. This full moon, the first of spring triggers Easter to fall this year on April 12th, on the later end of the range of possible Easter dates (from March 22 to April 25). (In 2008, Easter came very early on March 23rd due to an early spring full moon. That will be the earliest Easter in our lifetimes.) After full, our April moons rise about an hour later each night. On April 17th,  the moon again appears half full, but is then in the southern dawn sky. The  crescent moon appears near the bright planet Jupiter on the morning of 19th and close to the brilliant planet Venus at dawn on the 22nd. On April 26th, the crescent moon reappears low in the western dusk, close  to the 7 Sisters star cluster and the planet Mercury just below. As April ends, the evening moon is in Gemini and well placed for telescopic viewing.

Most of the bright planets are seen in April’s southeastern dawn. Venus blossoms in April as her rising time ahead of the sun increases from about an hour in early April to 90 minutes as April ends. Second in brightness is the planet Jupiter, appearing farther to the right and in the Southern dawn. (Both of these planets shine steadily, not twinkling as the night stars.) In the last half of April, you can see the dull planet Mars below Venus. Mars is less than 1% as bright as Venus due to its greater distance from us (now more than 6 times farther than Venus), smaller size, less reflective surface and greater distance from sun. Venus and Mars will appear closest on the morning of April 24th, then being 4 degrees (8 moon widths) apart.

The best evening planet in April is Saturn, shining high in the southern sky around 9 p.m. through April. Saturn nearly lies on a line from the bright star Spica (Virgo) lower in the Southeast and the bright star Regulus (Leo) higher in the South. Saturn is brighter than both stars, shining with a steady light; the ringed planet is 3/4ths of  the way from Spica to Regulus. A medium sized telescope magnifying 50 times or more should show Saturn’s rings as close to edgewise. If you can see the rings, then Saturn’s big moon Titan will be seen as a tiny star near Saturn. Titan is the second biggest moon in our solar system, orbiting Saturn every 16 days; Titan’s orbit is over 3 times bigger than our moon’s orbit about the Earth. In the second half of April, the innermost planet can be seen low in the western dusk. On April 26th, Mercury is setting at 8:45 p.m., more than 90 minutes after sunset. On this same evening, the crescent moon appears to the right of Mercury. On April 30th, Mercury appears just to the left of the 7 Sisters star cluster, low in the western dusk.   
The April program at the Frostburg State Planetarium is “Earth from Brightest Stars”, a view of the Earth as it would be seen from the more powerful stars of our night sky. This view of the Earth will take us back thousands to hundreds of years ago. Planetarium visitors can pick a free April sky chart at the Sunday programs that start at 4 p.m. and 7 p.m. on April 5th, 19th and 26th. (There will be no programs on Easter Sunday, April 12th.)

The Planetarium is in Tawes 302. Tawes is a modest building across from the large Compton Center, near the Lane University Center, and not far from the Performing Arts Center. To request a Planetarium bookmark, call (301) 687-7799 and leave your name and mailing address on the voice machine.         

By Dr. Bob Doyle

To contact Dr. Doyle, his mailing address is Planetarium, Frostburg State University, Frostburg, MD 21532 or by email at rdoyle@frostburg.edu.









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