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The Sky This Week, 2017 August 15 - 22

It's finally here!
Total Solar Eclipse of 29 July, 1878,
as depicted by Leopold Trouvelot at Creston, Wyoming Territory

The Moon moves through the stars of the Great Winter Circle this week, waning to a thin crescent that will then align perfectly with the Sun at New Moon, which occurs on the 21st at 2:30 pm Eastern Daylight Time. On the morning of the 16th Luna will rise just south of the bright star Aldebaran shortly after 1:00 am here in Washington. Over the next few hours before dawn she will drift apart from the star.

The Moon will cover the brightest star in the sky on August 21st. The solar eclipse that will occur on that day is probably the most anticipated astronomical event for North America and the United States of the past few decades. A total solar eclipse will span the country from Oregon to South Carolina, the first time we’ve had a coast-to-coast eclipse here since 1918. The last total eclipse to brush the "lower 48" states took place in February of 1979, tracing a path across Washington state, northern Idaho, Montana, and North Dakota. It’s a pretty safe bet that next Monday’s eclipse will likely be the most intensely observed astronomical event in history, as something like 20 million people are expected to pack themselves into the 70-mile wide swath of the umbral shadow as it scrawls across the nation. Many of us at the Observatory will be in the path of totality, distributed across the 14 states that the shadow will touch. Here in Washington, we will see about 81 percent of the Sun’s disc covered by the Moon. For us the eclipse begins at 1:18 pm EDT. Maximum eclipse occurs at 2:43 pm, then ends at 4:01 pm. The closest major city to Washington that will experience totality is Columbia, South Carolina, but if you plan to travel that way be prepared to camp by the roadside, since hotels and parks have been booked for months. If you plan to watch the eclipse from anywhere in the U.S., it is imperative that you do so safely! If you can’t find a set of "eclipse glasses", use indirect methods of viewing the event. Make a "pinhole" viewer, or use simple household items like colanders and cheese graters to project tiny images of the eclipsed sun onto a piece of white paper. Check in your local area for science centers, planetariums, and amateur astronomy clubs that will be holding eclipse observing parties.

Why do eclipses cause such a fuss? It’s hard to say. Having witnessed four myself, I can tell you that there are no other sights in the natural world that can compare to the few minutes that the Sun goes dark in the middle of the day. The remarkable coincidence of the Sun being 400 times larger than the Moon and 400 times farther away is unique to the Earth in our solar system; hypothetical residents of the other planets that share our star never see the remarkable phenomena associated with the event that we’ll see next week. And fortunately, if you miss this one, you’ll have another crack at a domestic total solar eclipse in April, 2024!

Jupiter lingers in the southwestern sky as evening twilight darkens the sky. Old Jove is still easy to spot even as he settles toward the horizon as the night passes. By the end of the week he sets at 10:00 pm EDT here in Washington, so whatever glimpse you can catch of him through the telescope won’t be in complete darkness.

Saturn takes over for Jupiter as the summer showpiece planet. The ringed planet is on the meridian during the time of evening twilight, and he is viewable in the telescope for several hours after darkness falls. Saturn is currently drifting slowly westward through one of the brighter star clouds of the Milky Way. This offers a very pleasing view through the telescope, especially if you’re in a dark location. The planet, surrounded by his bevy of moons, is set against a background of innumerable faint stars. Enjoy his setting with a low-power eyepiece on your telescope to enjoy him in the context of these myriad distant Suns.

Venus still graces the pre-dawn sky. This week she drifts past Castor and Pollux, the Twin Stars of Gemini, and the star Procyon in Canis Minor. On the morning of the 19th she receives a visit from the waning crescent Moon. Two days later, along the path of totality in the upcoming eclipse, Venus will appear briefly as the Sun turns night to day for those few precious moments.

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