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The Sky This Week, 2015 July 31 - August 25

Summer vacation skywatching, here we come!
Summertime Milky Way between Aquila and Sagittarius
Imaged with a Canon EOS Rebel T2i DSLR, 24mm @f/4, 30 seconds
@ ISO 6400 at Fishers Island, New York

"The Sky This Week" will be taking its annual summer break for the next few weeks. We’ll return to our regular weekly schedule on August 25th.

The "Blue Moon", aka the second Full Moon of July, occurred on July 31st at 6:43 am Eastern Daylight Time. Last Quarter will occur on August 6th at 10:03 pm EDT, New Moon on the 14th at 10:53 am EDT, and First Quarter on the 22nd at 3:31 pm EDT.

The highlight of August is the annual Perseid meteor shower, which peaks on the 12th and 13th. The shower is active from mid-July through late August, and early morning skywatchers can expect to see a few Perseids on any night during this period. The shower occurs as the Earth crosses the orbit of Periodic Comet 109P/Swift-Tuttle and runs into the debris sputtered off the comet’s nucleus during its 130-year journey around the Sun. The comet was co-discovered by Harvard College Observatory astronomer Horace P. Tuttle on July 18, 1862. In August of that year, when the comet was at its visual peak, he resigned his position at Harvard and joined the Union Army, fighting with the 44th Massachusetts Volunteer Militia. After surviving one campaign he joined the Navy, serving another 10 years as paymaster on a Union ship. He made occasional observations at the Naval Observatory, where he co-discovered Periodic Comet Tempel-Tuttle, progenitor of the annual Leonid meteor shower, in 1866.

The Perseid meteors will peak at a time when the moon is a very thin crescent in the morning sky, so conditions should be ideal for watching them. The best time to look is after midnight on the night of August 12/13. Find a place with a wide unobstructed view of the sky, lie down, and look up. If the weather is clear and you’re in a dark location, you may see 50 to 75 meteors per hour!

Venus and Jupiter are now lost in the glare of evening twilight. Both planets reach conjunction with the Sun during August. Venus will pass between the Earth and Old Sol on the 15th, while Jupiter slips behind the Sun’s disc on the 26th.

The only bright planet left in the evening sky is Saturn, which can be seen in the southwestern sky as evening twilight deepens. The ringed planet sets at around 1:20 am as August opens. By the 21st he slips below the horizon at midnight. The ringed planet reaches the second stationary point in the current apparition on August 2nd. Over the course of the next few weeks he’ll begin creeping eastward toward the stars in the head of Scorpius. He remains a fine sight in the telescope, with his rings tipped 24 degrees toward our line of sight.

If you’re vacationing away from the city, the summer Milky Way shines overhead at the midnight hour for the month of August. As we gaze toward the tail of Scorpius and the "spot" of the teapot-shaped asterism in Sagittarius we’re looking toward the galactic center through dense clouds of stars and gas. These star clouds are some of the most intriguing sights you can enjoy with steadily-held binoculars and small low-power telescopes. The numbers of stars you’ll run into is simply enormous, and sprinkled among them are bright knots of glowing gas and star clusters of many forms. I’ll be spending many evenings out in a lawn chair taking in the view.

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