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The Sky This Week, 2018 April 3 - 10

April is Astronomy Month...no fooling.
The Moon rising through trees
The Full Blue/Sap/Egg/Paschal Moon rising through trees, Alexandria, VA on 2018 March 31,
imaged with a Canon EOS Rebel T2i DSLR, 250mm @ f/8, HDR composite of exposures of 1/20, 1/80,1/320, and 1/640s, ISO 800.

The Moon swings low along the southern reaches of the ecliptic this week, wending her way past the morning parade of bright planets that are drifting through the summer constellations.  Last Quarter occurs on the 7th at 3:17 am Eastern Daylight Time.  Luna starts the week just to the east of bright Jupiter, then cozies up to Mars and Saturn on the morning of the 7th.  By the week’s end she moves into the dim star fields of the rising autumnal constellations.

April is Global Astronomy Month, an annual celebration of sky awareness sponsored by Astronomers Without Borders.  Celebrating “One People, One Sky”, the next few weeks will see a number of events to increase the general public’s appreciation of the universe as seen from our humble planetary home.  There are many ways to participate in the month’s activities from composing sky poetry to turning our lights to help promote a view of a darker sky.  The month incorporates International Dark Sky Week from the 15th through the 21st, and culminates in Astronomy Day, which takes place Saturday, April 21st.  On this day amateur astronomy clubs around the world will congregate at local parks with telescopes and hands-on activities to bring the stars to anyone with an interest in exploring them.  We’ll list events in the Washington, DC area as the date approaches.  

Winter’s bright constellations linger in the early evening sky.  By the end of evening twilight at around 9:00 pm, you can still find Orion in the southwestern sky surrounded by the bright stars of the Great Winter Circle.  Act quickly if you want to view celestial gems like the Pleiades or the Great Orion Nebula; they both set well before midnight.  At this time look for the twin stars of Gemini, Castor and Pollux high in the west and the star Regulus in Leo to the east of the meridian.  In between these two constellations is a small group of 3rd and 4th magnitude stars that mark the location of the Zodiacal constellation of Cancer, the Crab.  The constellation itself is not much to look at, but if you point a pair of binoculars toward it you’ll see a scattered group of several dozen stars that make up the star cluster known as “The Beehive” or the “Praesepe”.  Under dark skies you can see it as a nebulous patch of light, and it was one of the first such “nebulae” to be investigated by Galileo with his primitive telescope in 1609.  He was able to resolve it into about 40 stars, and you should be able to see that many in binoculars.  Large telescopes reveal about 1000 cluster members, most of which are very low-mass red dwarf stars.  It lies about 580 light-years from us and is one of the closest large star clusters to the solar system.  

As the midnight hour approaches the brighter stars of spring begin to take over the night.  Regulus and his companions in Leo are near the meridian, and the Big Dipper Asterism can be found almost directly overhead.  You can follow the arc of the Dipper’s “handle” to the bright star Arcturus, the fourth-brightest star in the sky, then “drive a spike” to Spica, the brightest star in the sprawling constellation of Virgo.

The evening twilight hour is dominated by the dazzle of the bright planet Venus, which shines high in the west.  She becomes visible within minutes of sunset in a clear sky and remains visible until after 9:00 pm.

Giant Jupiter rises at around 10:30 pm and should be easily visible in the southeast by midnight.  Old Jove is now second only to Venus in brightness and will move into better evening visibility over the course of the month.  He is currently drifting westward among the stars of another faint Zodiacal constellation, Libra, the Scales.  

Early risers still get the best views of Mars and Saturn, which are currently located just above the top of the “Teapot” asterism in Sagittarius.  They start the week just over a degree apart, but over the course of the week Mars drifts eastward from the ringed planet.  They will be five degrees apart by the week’s end.  Look for a great pre-dawn photo opportunity on the morning of the 7th, when the last quarter Moon joins the planetary pair.

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