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The Sky This Week, 2019 April 2 - 9

Embracing dark skies...
Messier 81 and 82, galaxies in Ursa Major.
Messier 81 (right) and 82, galaxies in Ursa Major
Imaged 2016 December 31 with an Explore Scientific AR102 102mm (4-inch) f/6.5 refractor
and a Canon EOS Rebel T2i DSLR from Mollusk, Virginia.

The Moon returns to the evening sky this week, with New Moon occurring on the 5th at 4:40 am Eastern Daylight Time.  Luna will climb quickly in the western sky as the week progresses, passing near ruddy Mars and the bright star Aldebaran on the evenings of the 8th and 9th.

This week we continue the observance of International Dark Sky Week, which occurs every spring to raise awareness of our ever-brightening night skies.  Created in 2003 by then high-school student Jennifer Barlow, the 16th observance closes out on April 7th.  Over the years the event has taken on a global presence, starting with Jennifer’s simple idea: “I want people to be able to see the wonder of the night sky without the effects of light pollution. The universe is our view into our past and our vision into the future. … I want to help preserve its wonder.”  You can support the efforts of International Dark Sky Week by visiting their website and working within your community to raise awareness of light pollution and the relatively easy steps that can be taken to lessen its effects.  Your efforts will help to promote the idea that we don’t have to sacrifice our views of the night sky and still have safe places to live and work.  The Naval Observatory’s station near Flagstaff, Arizona has benefitted by such community awareness since 1955.  Today Flagstaff remains the world’s first International Dark Sky Community, a designation that it earned in 2001.  Since it passed its first outdoor lighting ordinance in 1958 Flagstaff has demonstrated that dark skies and safe neighborhoods can peacefully coexist.

Our current nighttime sky is one of transition.  During the hour after the end of evening twilight the bright constellations of winter still linger in the west.  Most prominent of these is Orion, the Hunter, whose bright stars beam down on us from above the southwest horizon.  Surrounding Orion are the bright stars that make up the Great Winter Circle.  From a dark location you should be able to see the soft glow of the Milky Way passing through the heart of the circle.  There are a number of fine objects to find in the star clouds that delineate our home galaxy.  The famous “Great Nebula” in Orion glows in the middle of a small asterism know as “The Sword” that seems to hang below Orion’s distinctive “belt”.  Another fine star cluster, Messier 41, can be glimpsed just below the dazzling light of Sirius, the brightest star in the sky.  High in the west locate the bright yellow-hued star Capella, brightest star in the constellation of Auriga, the Charioteer.  Three bright star clusters, Messier 36, 37, and 38 may be found between Capella and El Nath, the star that marks the northern “horn” of Taurus, the Bull.  Bright stars and star clusters are characteristic of areas of the sky near the Milky Way, but as the night hours pass our view is directed away from the Galaxy’s plane.  

By 11:00 pm we find the constellations of Leo, the Lion and Ursa Major, the Great Bear taking center stage.  We see many fewer bright stars as we gaze out into space past these star patterns, and binoculars show many fewer “deep sky” objects.  However, modest telescopes can show us something that is not only extraordinary but also extra-galactic.  Here we find the “realm of the galaxies”, which lie beyond the stars of Leo, Ursa Major, and the rising stars of Virgo.  On clear dark nights such instruments reveal dozens of small amorphous globs of light, and in some places several appear in the same telescope field.  These are remote galaxies like our Milky Way, located at almost unfathomable distances.  Most of these flecks of light belong to a vast cluster of galaxies of which our Milky Way is a far outlying member.  The core of the Virgo Cluster is dominated by a few huge galactic systems, Messier 84, 86, and 87, each of which has a mass of over one trillion Suns!  They are so far away that their light began its journey toward us when the dinosaurs became extinct.

Mars continues to wend his way through the stars of Taurus, the Bull.  This week the red planet passes between the Pleiades star cluster and the bright star Aldebaran.  Look for the waxing crescent Moon near Mars on the evenings of the 8th and 9th.

Jupiter rises at around 1:00 am by the end of the week, and the best time to see him is still just before the onset of morning twilight.  He is located in the south at this time, between the stars of Scorpius and Sagittarius. 

Saturn is also best seen before sunrise.  He, too is located in the southern sky and may be found just to the east of the “teapot” asterism of Sagittarius.

Venus appears low in the southeast, rising during morning twilight about an hour and twenty minutes before the Sun.  Catching a glimpse of her will be difficult; you’ll need a very clear sky and a low horizon to do so.

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