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The Sky This Week, 2019 July 2 - 9

Has it really been 50 years?
Scorpius, Jupiter, and the Milky Way, imaged 2019 June 21 from Fishers Island, NY
Scorpius, Jupiter, and the Milky Way, imaged 2019 June 21
with a Canon EOS Rebel SL2 DSLR from Fishers Island, New York.
Note the star clouds of the summer Milky Way to the left of Jupiter.

The Moon returns to the evening sky this week, waxing through her crescent phases as she moves through late spring’s constellations.  First Quarter occurs on the 9th at 6:55 am Eastern Daylight Time.  Luna may be found three degrees north of the bright star Regulus in the constellation of Leo, the Lion on the evening of the 5th.  On the 8th, look for the Moon just under two degrees from the second-magnitude star Porrima in the constellation of Virgo.  If you have a telescope, give Porrima a look.  It is a close double star located just 38 light years from Earth.  The two components orbit each other with a period of 169 years, so it is possible to see changes in the separation and position angle of the stellar pair on a year-to-year basis.  In 2005 an 8-inch telescope was required to split the pair at their closest separation.  Now they should be relatively easy to divide with a 4-inch instrument.

It is hard for me to believe that 50 years ago I was a witness to one of the greatest voyages of exploration in history.  From July 16 until July 24, 1969 the world watched as three astronauts rode the world’s most powerful rocket into Earth orbit, then pressed on to the Moon.  Like many people at that time I was glued to the television, seemingly riding along with Neil Armstrong, Edwin Aldrin, and Michael Collins as they embarked on the first attempt to touch the surface of another world.  On the night of July 20th, as the Lunar Module “Eagle” rested on the surface of the Sea of Tranquility, I set up my small telescope in the back yard and gazed at the Moon as I had on dozens of evenings before.  However, this time it was different; although I couldn’t see them, I was aware that two people were in the field of view, somewhere in that battered landscape that I had come to know so well.  Fifty years later I still look at the Moon, and I still see it in that same “different light” that I did in 1969.  Since that warm July evening five more Apollo missions and ten more people have walked on the Moon, and we continue to probe its surface with orbiters and robotic landers.  This week you can see the Moon in approximately the same phase as it was when Armstrong and Aldrin landed.  Set up your telescope on the evening of the 7th and you’ll see conditions very similar those I enjoyed 50 years ago.  Don’t expect to see any artifacts of our presence, though.  Even the largest optical telescope on the Earth can’t resolve anything smaller than a football stadium!

Early in the week, after the crescent Moon sets, late-night skywatchers can enjoy the splendor of the rising summer constellations and the Milky Way, which arcs across the eastern sky like a diaphanous rainbow.  The luminous band intersects the southern horizon in a series of star “clouds” interspersed with mottled patches of darkness.  This region of the Milky Way marks the center of our home galaxy which lies over 30,000 light years distant from our galactic outpost.  We can’t directly see the blazing core of the galaxy itself due to enormous clouds of opaque gas and dust that waft through the galactic plane, but we can see the glowing patches of luminous gas and clusters of stars that result from the concentration of some of these dark clouds.  Take a few moments to look at these distant glowing clouds and try to visualize the sheer number of stars that they contain.  You can start to resolve some of these clouds with binoculars, but my favorite instrument for viewing the Milky Way is my small low-power telescope.  

As you wait for your local fireworks display on the evening of the 4th, look for the slender crescent Moon low in the western sky.  At 9:00 pm Luna will be about 15 degrees above the horizon, and if you sweep the sky below and to the right of the Moon you might be able to catch a final glimpse of mars and Mercury before they disappear into the solar glare.

Jupiter commands your attention in the southeastern sky as evening twilight settles over the landscape.  By 10:30 the last remnants of twilight disappear, and if you’re in a dark location you you’ll find Old Jove basking in the glow of the Milky Way.  

Saturn reaches opposition from the Sun on the 9th.  On this date he will rise at sunset and set at sunrise.  The ringed planet follows Jupiter across the sky above the southern horizon, and, like Old Jove, never climbs very high in our sky.  You’ll need a night of steady air to glimpse Saturn in detail, but often the sultry nights of July and August can provide the best conditions for a stunning view of this far-flung world.

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