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The Sky This Week, 2011 July 12 - 19

The end of an era

Trail of the International Space Station passing
over the George Washington Masonic Memorial

Alexandria, VA, 2011 June 29, 22:12 EDT

The Moon brightens the sky for late-night and early morning skywatchers this week, scudding above the southern horizon as she wends her way through the constellations of summer an early autumn. The Full Thunder Moon occurs on the 15th at 2:40 am Eastern daylight Time. On the night of the 13th she may be found just above the "Teapot" asterism formed by the brighter stars of the constellation of Sagittarius. On the 15th use binoculars to try to spot the third-magnitude star Dabih just over a degree above Luna’s brilliant full disc. Dabih shows a faint companion in binoculars and marks the head of Capricornus, a mythical creature of the Zodiac that’s half goat and half fish!

This week marks the end of an era in the chronicle of human space flight as the Space Shuttle Atlantis completes its final mission. It’s hard to believe that the first humans to venture outside of earth’s protective atmosphere did so 50 years ago, and the Shuttles have been flying for the past 30 years. Originally conceived to be a sort of "space truck" that promised near-routine access to low-Earth orbit, the five orbiters built over the program’s lifetime aimed for the high ground of both technological development and mission complexity. Flying the shuttles may have had the appearance of being "routine", but these were probably the most complex machines ever built, and on two occasions we were starkly reminded of their incredible fragility. While they never met their ultimate goal of cheap access to space, they still carried out a broad spectrum of missions and ferried over 700 people into space. The main legacy of the Shuttle era is the International Space Station, which has been continuously occupied since November 2000. The ISS structure spans the length of a football field, and it is the brightest artificial object that can be seen in the night sky. On many occasions over the past decade we’ve had opportunities to see the Shuttles and ISS pass overhead in formation. These days have now ended. Unfortunately for this final flight orbital geometry will prevent us from seeing Atlantis and the Space Station together. However, the ISS should remain operational for at least another 10 years, so there will be many sighting opportunities to come to remind us of what the shuttle program accomplished. You can track the ISS, as well as a variety of other bright objects in low-earth orbit, at a website called "Heavens Above".

For those seeking more far-flung targets, you still have an opportunity to catch a glimpse of the planet Saturn in the evening sky. The ringed planet may now be found in the southwest as evening twilight deepens, and it is during this time of fading light after sunset when you’ll get your best views through the telescope. Evening astronomical twilight now ends at around 10:30 pm, and by this time Saturn is only some 20 degrees above the horizon, so you’ll be viewing him through lots of turbulent July air. However, almost any telescope will reveal the planet’s rings, which are gradually opening up to reveal more of their northern face. If the air is particularly still you should still be able to sight several of his ice-bound moons in a modest instrument.

Saturn now sets at around midnight, but you don’t have to wait too much longer for his replacement. Giant Jupiter rises by 1:00 am as the week ends, and the planet continues to advance toward the evening sky rising four minutes earlier on each successive night. Old Jove is high in the southeast as morning twilight begins, and many amateur astronomers are setting their alarms for good morning glimpses of Jupiter in their telescopes. Few sights in the solar system are as changeable as Jupiter, so morning forays are almost always worth the effort.

If you’re up between 4:30 and 5:00 am, look toward the gradually brightening eastern horizon for the faint ruddy glow of Mars. The red planet spends this week coursing among the stars of Taurus, the Bull. You can find him about 8 degrees east of the ruddy star Aldebaran. The gap between the two increases to about 12 degrees as the week passes.

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