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The Sky This Week, 2017 June 13 - 20

The last week of spring?
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Jupiter with Three Moons
Imaged 2017 June 11, 02:01 UT in good seeing from Alexandria, Virginia

The Moon spends the week crossing the faint constellations of the autumn sky during the early morning hours. She wanes through the Last Quarter phase, which occurs on the 16th at 3:26 pm Eastern Daylight Time. You’ll have to wait until the end of the week before Luna encounters any bright objects. You’ll find her near dazzling Venus on the mornings of the 20th and 21st.

The June campaign for the Globe at Night citizen-science observing program opens its June "window" on the 16th and continues for the following 10 nights. This program is a great way to not only learn to recognize constellations, it also benefits our understanding of how artificial night lighting is spreading around the world. This month’s featured constellation is Hercules, which occupies a sizeable patch of the sky between the bright stars Arcturus and Vega. Although it is a large star pattern, most of its stars are second- and third-magnitude. The center of the constellation is made up of a trapezoid of stars known as The Keystone which forms its most prominent feature. The entire constellation is best seen from darker skies, so it’s ideal for viewing from favorite vacation spots at the shore or the mountains. Visit the Globe at Night website for finder charts and to report your findings. You’ll join nearly 10,000 others who have already reported their observations so far this year.

The summer solstice will occur on the 21st at 12:24 am EDT, but this week we see the earliest sunrises for the year in mid-northern latitudes. Here in the Washington, DC area Old Sol crests the horizon at 5:42 am EDT for the next several mornings before reversing the trend beginning on the morning of the 17th. These early sunrises are offset by the occurrence of later sunsets, which reach their latest for the year on June 24th. This makes June 20th and 21st the year’s longest days, with the Sun above the horizon for 14 hours and 54 minutes. Throwing in the times of astronomical twilight, skywatchers only have just over four hours of total darkness to enjoy completely dark skies.

Take advantage of those dark skies and get away from the city’s heat and smog to enjoy the rising summer Milky Way during the short hours of darkness. The galaxy’s brightest section begins crossing the meridian to the south by 1:00 am, and you’ll have a great view of the star-clouds in the Summer Triangle of bright stars for the rest of the night.

Jupiter now crosses the meridian at sunset, limiting his best visibility to the late twilight and early dark hours of the night. This still gives you several hours to get a good look at him through the telescope, and the view is still worth your while. The planet’s unique feature, the Great Red Spot, can be seen rotating across the planet’s disc on the evenings of the 13th, 15th, and 18th between 9:30 and 10:30 pm. On the evening of the 19th the Moon Io will cast its shadow on Old Jove’s cloud tops.

Saturn reaches opposition on the morning of the 15th. He will rise at sunset, transit the meridian at 1:00 am, and set at sunrise. Look for an interesting phenomenon a few nights on either side of opposition where the planet’s rings appear noticeably brighter than the ball of the planet. Known as the Seeliger Effect, this is a result of the Sun’s full illumination of ring particles and is similar to the brightening of our Moon at the time of Full Moon.

Venus hangs in the east in the pre-dawn sky. You’ll have no trouble finding her as morning twilight begins to gather. She holds court with the Moon on the mornings of the 20th and 21st.

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