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The Sky This Week, 2015 May 5 - 12

Dipping into the spring sky.
Jupiter and two moons, 2015 May 4, 01:55.5 UT

The Moon wanes in the overnight hours this week, coursing through the stars of summer as the make steady inroads into the evening sky.  Last Quarter occurs on the 11th at 6:36 am Eastern Daylight Time.  Luna begins the week among the stars of Scorpius and Sagittarius, then moves into the sparse star fields of autumn’s dim constellations.

As the Moon wanders into the morning sky, the springtime constellations become easier to trace out in the evening.  You should be able to easily identify the Big Dipper high in the northern sky as evening twilight ends.  This time of the year is also the perfect time to look for the more elusive stars of the Little Dipper.  Find the two stars that form the outer edge of the “bowl” of the Big Dipper, which stand almost vertically at around 9:30 pm.  These two stars, Merak and Dubhe, are commonly called “The Pointers” since a line passing through them and extending toward the horizon point directly to Polaris, the North Star.  Polaris marks the end of the “handle” of the Little Dipper, which curls eastward under the other stars of the Big Dipper.   Most of the Little Dipper’s stars are quite faint, and serve as a good measure of the darkness of your observing site.  If you go back to The Pointers and extend the line through the zenith, the southward, you’ll run into the constellation of Leo, the Lion, led by the bright star Regulus.  Now go back up to the Big Dipper and follow the curve of its “handle”.  This “arc” will lead you to Arcturus, the brightest star in the northern hemisphere sky.  Rosy Arcturus is the brightest star in a large constellation that the ancients would like you to believe represents an old man leaning on a staff holding two dogs on a leash!  This group is called Boötes, the Herdsman.  I find it much easier to spy a large ice-cream cone with Arcturus marking the cone’s tip.  The generous scoop of ice cream (insert your favorite flavor here) occupies the area off the end of the Dipper’s handle.

The evening twilight time showcases the dazzling planet Venus and the more subtle glow of Mercury.  You’ll have no trouble locating Venus, but Mercury will take a little effort to track down.  The fleet planet lies about 20 degrees below and to the right of Venus in fading twilight and you might want to use binoculars to locate him.  He will move toward and about 8 degrees north of the star Aldebaran during the course of the week, gradually fading after he passes greatest elongation east of the Sun on the 6th.  By the end of the week he will begin to turn back toward the Sun.  His next favorable evening apparition won’t occur until the end of the year.

Venus dominates the twilight sky and remains above the horizon for a couple of hours after the sunset glow fades.  This would be a good week to try to observe one of the planet’s more subtle effects.  If you find yourself in a dark site where you can see the stars of the Little Dipper, hold a piece of paper up and hold a finger between the paper and Venus.  You should be able to see a faint shadow of your finger on the paper!

Jupiter spends the evening hours in the western half of the sky, but he still gives Venus a run for her money.  Through the telescope he is much more interesting to look at than his more brilliant rival.  On the evening of the 8th you’ll have a ringside seat to see the planet’s famous Great Red Spot, which will be almost in the center of the planet’s disc at 9:30 pm.  On the evening of the 10th you can watch the moons Io and Europa converge and merge into a single object just before 10:00 pm.

Saturn rises shortly before the waning Moon on the evening of the 5th.  By the weekend the ringed planet comes up at around 9:00 pm.  He’s high enough to train the telescope on by the late evening hours, and after Jupiter provides the best view for small to modest telescopes.  On a good clear night the view of the planet, set in its rings and surrounded by the faint glow of half a dozen tiny moons is one of the most interesting sights in all of Nature.



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