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The Sky This Week, 2013 July 9 - 16

Months by the Moon
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Saturn, 2013 July 7, 02:14 UT 


The Moon works her way back into the evening sky this week. First Quarter occurs on the 15th at 11:18 pm Eastern Daylight Time. Luna wends her way through the springtime constellation in the western sky as twilight deepens, passing a number of bright objects as she goes. Her first target is bright Venus, which you’ll find about seven degrees north of the Moon on the evening of the 10th. The next evening finds her six degrees south of the star Regulus in the constellation of Leo, the Lion. On the 15th you’ll see the bright star Spica just over a degree to the northeast of the Moon’s dark limb, and on the 16th she passes just four degrees south of golden Saturn.

This is another good week to take a few moments each evening to explore our only natural satellite. As her phase increases a steady stream of interesting features are revealed by the advancing terminator line. Many of us who grew up in the heyday of the "Space Age" will remember the atmosphere of a July week in 1969 when the voyage of Apollo 11 began on the 16th. Since that time some 44 years ago my perception of the Moon has been forever changed. Where once I saw a distant place quivering in the eyepiece of a small telescope on a warm summer evening I now see a destination that we have visited and touched with our hands and minds. The Sea of Tranquility, the Fra Mauro highlands, Hadley Rille, and the Taurus-Littrow valley are now almost as familiar to me as my neighborhood, and I enjoy visiting them every month.

The sighting of the first lunar crescent should occur at dusk on the 9th. This event signals the beginning of the Islamic holy month of Ramadan, which will last until the next sighting of the crescent in early August. The Islamic Calendar is a strictly lunar calendar rigidly tied to the phases of the Moon. The 12 lunar months fall some 11 days short of a mean solar year, so Islamic months regress through the seasons over a 33-year period. Next year Ramadan will begin in late June.

Bright Venus is slowly working her way eastward from the glare of the Sun, but she is still only visible during evening twilight. She actually sets a bit earlier on successive evenings, but the Sun is also setting earlier, so the net effect is that she seems to hold her own against Old Sol. By early September she will finally set at the end of evening twilight, and from then until the end of the year you’ll have the chance to see her against a dark sky. In the meantime, keep an eye on her over the next two weeks as she closes in on the bright star Regulus. On the evenings of the 21st and 22nd she’ll pass just over a degree north of the star.

Saturn pops into view west of the meridian as twilight fades about half an hour after sunset. The ringed planet is still well-placed for observation during the first couple of hours of darkness, but you’ll need to catch him in the eyepiece before he settles into the horizon haze. Saturn’s rings are generously tipped in our direction, so they should be easy to see in small telescopes and binoculars, and the shadow of the planet’s disc falling on the rings gives Saturn a three-dimensional appearance in modest scopes. As always, an increase in aperture will show more detail. I recently upgraded the main telescope at my home observatory from 8 inches to one of 9.25-inches aperture, and the difference is quite remarkable!

For those of you vacationing away from the city lights, you still have the late night and early morning hours to explore the glorious summer Milky Way. Binoculars and a lawn chair will provide you with all you need to unlock the secrets of our galaxy’s billowing star clouds. Sweeping up from the southern horizon through the heart of the Summer Triangle (made up by the bright stars Vega, Deneb, and Altair) you will pass by dozens of bright knots of stars and glowing nebulae, all set against a backdrop of millions of distant suns. The area between Vega and Deneb is now of particular interest to astronomers. It is this area which has been under constant scrutiny for the past several years by NASA’s Kepler space observatory. By "staring" at 145,000 stars in this part of the galaxy Kepler has confirmed the existence of over 100 "exoplanets", with some 3000 more candidates awaiting further analysis. You probably won’t discover any new planets from your lawn chair, but you’ll certainly see a lot of stars!

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