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The Sky This Week, 2019 June 4 - 11

Twilight is time for the Moon
Region of Tranquillity Base, landing site of Apollo 11, imaged with a Celestar-8 Schmidt-Cassegrain telescope from Alexandria, Virginia
Region of Tranquillity Base, landing site of Apollo 11
imaged with a Celestar-8 Schmidt-Cassegrain telescope from Alexandria, Virginia.

The Moon returns to the evening sky this week, waxing through her crescent phases as she progresses through the springtime constellations. First Quarter occurs on the 10th at 12:59 am Eastern Daylight Time. Look for Luna close to the bright star Regulus in Leo on the evening of the 8th.

June is the month of the shortest nights in the Northern Hemisphere. While most of us revel in the lazy evening hours of early summer, those of us who revel under the fainter lights of the overnight hours must carefully weigh our desire for darkness with the realities of our diurnal lives. Looking back at my observing logbooks from the past few decades I find very few that occur around the time of the summer solstice. This is unfortunate, since many of the most interesting objects in the night sky are well-placed for viewing at this time. Most of these objects are distant galaxies, which are liberally scattered over much of the current sky. The seeming lack of "near-sky" objects in the form of bright stars and distinctive constellations is offset by the sheer number of distant swaths of faint light that betray the presence of hundreds of billions of stars at near-unfathomable distances. Viewing these far-flung star cities requires dark skies and rested eyes, and with twilight ending well after 10:30 pm and a scant four hours of complete darkness available it is difficult to get inspired to pack up the telescope and venture to locations well away from city lights.

Fortunately, the Moon returns to give us a great place to explore in the twilight hours. If we can’t stay up late enough to enjoy light from a hundred million light-years away, then our closest celestial neighbor offers an easy target to enjoy from the comfort of the front yard. Luna is a mere 1.3 seconds away at the speed of light, and it is the only celestial object that offers features that we can see on a scale that most of us can understand. I hope to enjoy many evenings with the Moon in the eyepiece over the next couple of months as we gear up for the 50th anniversary of the landing of Apollo 11. While the artifacts of the lunar landings are impossible to see with any earthbound telescope, it is possible to see the areas where the twelve astronauts who ventured to the surface left their boot prints in the ancient lunar dust. Tranquillity Base, the landing site of Apollo 11, is well-placed for viewing in modest telescopes on the evening of the 8th. If you have a good lunar atlas (and there are many available online) it is located near the northern edge of the Sea of Tranquillity between the small crater Moltke and the twin formations of Sabine and Ritter. This site was chosen because it appeared to be flat and smooth in images from unmanned orbiters, but Armstrong and Aldrin found it to be much more rough than anticipated. While later Apollo flights landed in more geologically interesting places, those first images from the lunar surface still come to mind every time I look at this area with my telescopes.

Over the course of the past year ruddy Mars has managed to stay ahead of the relentless Sun. During this time he has travelled almost halfway around the sky, but this week he is no longer visible after the end of evening twilight. You can still find him about an hour after sunset, about 10 degrees above the western horizon and 10 degrees below the twin stars of Gemini, Castor and Pollux. Toward the end of the week Mars is joined by Mercury, which moves to within five degrees of the red planet by the week’s end.

Jupiter reaches opposition on the 10th, when he is located opposite the Sun in the sky. This is when the giant planet rises at sunset and sets at the following sunrise, with peak visibility occurring at around 1:00 am. However, with the Sun near his most northerly declination as he approaches the solstice, this means that Old Jove is at his most southerly declination on the opposite side of the ecliptic. This makes viewing Jupiter a bit difficult from northern climes, but that handicap is offset by Jupiter’s closest approach to Earth at the same time. Jupiter has been putting on quite a show for patient observers this year, with radical changes taking place in the famous Great Red Spot, which seems to be "unravelling" before our very eyes.

Saturn follows Jupiter into the sky, rising at around 10:30 pm. He will come into opposition in another month, showing his distinctive rings as he slowly drifts against the stars just east of Sagittarius.

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