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The Sky This Week, 2019 May 14 - 21

Full Moon, Spring Stars.
Full Moon, 2017 December 4
Full Moon, 2017 December 4, 02:52 UT
imaged with an Explore Scientific AR102 102mm (4-inch) f/6.5 refractor
and a Canon EOS Rebel T2i DSLR from Alexandria, Virginia.

The Moon brightens the late spring sky as she dives toward the southern reaches of the ecliptic this week.  Full Moon occurs on the 18th at 5:11 pm Eastern Daylight Time.  The 18th also happens to be the 50th anniversary of the launch of Apollo 10, the “dress rehearsal” for the subsequent landing of Apollo 11 in July of 1969.  Apollo 10 tested all of the rendezvous and docking maneuvers leading up to the landing and approached to within 16 kilometers (10 miles) of the lunar surface, proving that the Apollo hardware was ready for the first crewed landing of Apollo 11.  Two of the crew members, John Young and Gene Cernan, subsequently returned to the Moon, commanding Apollos 16 and 17, respectively.  Look for the Moon close to the bright star Spica on the evenings of the 15th and 16th.  On the 18th she stands just north of the stars that form the “head” of Scorpius.  As the week closes she passes by the bright glow of the giant planet Jupiter.  

The springtime constellations of Leo and Ursa Major hold court as evening twilight fades.  We now have to wait until 10:00 pm for full darkness to fall, and by this time Leo lies west of the meridian.  Its brightest star, Regulus, may be found high in the southwest at the base of an asterism popularly called “The Sickle”.  Just above Regulus is the star Algieba, which is a great target for the small telescope.  Appearing as a single second-magnitude star to the unaided eye, the telescope reveals a pair of gold-hued stars in close proximity.  The pair orbit each other with a period of about 510 years and are located 130 light-years from Earth.  Turning your attention to the north, you’ll see the seven stars of the “Big Dipper” asterism crossing the meridian.  While none of the seven stars that make up the Dipper are brighter than second-magnitude, this is still one of the most recognized star patterns in the entire sky.  They are the brightest stars in the constellation of Ursa Major, the Great Bear, but you need a good dark sky to see the rest of this sprawling constellation.  With the Moon brightening the sky your explorations will be limited to the brighter members, but there are nonetheless objects worth hunting down.  One of my favorites is the star Mizar, which marks the “bend” in the Dipper’s “handle”.  Close to the star is a faint companion, Alcor, which was once used as a test of keen eyesight.  Through the telescope you’ll see that Mizar is itself a double star, the first of its kind to be discovered by the astronomer Giovanni Riccioli in 1650.

High in the east you can’t help but notice the bright rose-tined star Arcturus, the brightest star in the northern hemisphere of the sky.  Arcturus leads the constellation of Boötes, The Herdsman, which occupies the patch of sky between the end of the Dipper’s handle and the bright star.  The constellation’s second-brightest star, located to the northeast of Arcturus, is known as Izar (not to be confused with Mizar in Ursa Major!)  This is another treat for the telescope, and it will prove to be a good test of the quality of your instrument.  A good 3-inch telescope should resolve the two components, which have striking yellow and blue tints.  The great Russian double-star observer Otto Struve gave it the name “Pulcherimma”, Latin for “the loveliest”, and once you’ve seen it you’ll understand his sentiment.  It is one of my favorite double stars in the sky.  Izar is just over 200 light-years from us, and the stars orbit each other with a period of some 1000 years.

Mars continues to linger in the west after sunset, drifting eastward among the stars that form the “foot” of Castor, one of the Gemini twins.  This week the red planet skirts just north of the galactic star cluster Messier 35 on the evenings of the 18th and 19th.  Binoculars should show the cluster as a hazy patch, but a small telescope should resolve it into dozens of stars.

Giant Jupiter rises just after 10:00 pm in the southeast, and by midnight you should have a good view of him low in the southeastern sky.  He’s located about 13 degrees northeast of the bright reddish star Antares, brightest star in the constellation of Scorpius.  He will reach opposition in another month.

Saturn follows Jupiter into the sky, rising shortly after midnight.  The ringed planet will reach opposition in early July and will join Jupiter as the summer’s showpieces.  Both planets will bask in the rich star clouds of the summer Milky Way.

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