Skylights featured on Astronomy Picture of the Day

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Skylights featured six times on Earth Science Picture of the Day:
1 , 2 , 3 , 4 , 5 , 6


Photo of the Week. Continuous lightning over the sea furiously backlights the clouds that created it. (Second in a series of three. See number 1.)

Astronomy news for the week starting Friday, September 1, 2006.

With a couple of good exceptions, this seems to be a week for the outer planets, which might then be appreciated even if unseen. First, though, comes the Moon, which spends most of the week waxing through its gibbous phase, fattening to full, which is passed on Thursday, September 7 (yes, it is September, time to think about fall, which begins this year in North America on September 22). On Tuesday the 5th, the Moon passes a few degrees to the south of Neptune (still in far-eastern Capricornus), and then on Thursday the 7th much closer to the south of Uranus (in Aquarius, 10 degrees southeast of the "Water Jar"). The planet is actually occulted by the Moon as seen from Australia.

Then the Moon takes on the Earth's shadow, at full phase clipping it for a partial eclipse. Unfortunately it takes place in early afternoon for North America with the full Moon out of sight. Europeans and Africans, however, will get a fine view of it. Not that it will be very impressive, as only a tiny northern section actually gets into full shadow.

Uranus is now at its best, passing opposition with the Sun on Tuesday the 5th, when it rises at sunset, crosses the meridian at midnight, and sets at sunrise. Just shy of fifth magnitude, the planet is visible to the naked eye in a dark sky, and is an easy object in binoculars: providing you can position it on an atlas among the stars. By odd coincidence, at almost the same hour Pluto ceases retrograde (westerly) motion, the planet (which can stray far from the ecliptic) close to the juncture where Serpens Cauda, Ophiuchus, and Sagittarius all come together.

Planet or not? Traditionally called a planet (since its 1930 discovery by Clyde Tombaugh), Pluto is the leading member of the Kuiper Belt, a broad region of planetary debris that extends far beyond Neptune. Though barely second largest after "Xena" (2003 UB313) it is much closer, a small portion of its orbit dipping inside Neptune's. The International Astronomical Union has just dropped Pluto from its status as official "planet." In many minds and hearts, however, it will unofficially remain in its own unique category as "honorary planet."

With the naked eye, you still have Venus to admire. The bright planet rises in early morning twilight around 5:30 AM, with much dimmer Saturn to the west of it. While a quarter as bright as Venus, Jupiter stands out the better, as it is so nicely visible in the early evening (in Libra, just northwest of Zubenelgenubi) in a dark southwestern sky. Setting ever earlier, however, it is now down and out of sight by 10 PM, leaving the sky devoid of any of the classical ancient planets.

This is a fine time of year to admire the vastness of Ophiuchus, the Serpent Bearer (wrapped with Serpens itself). The constellation looms like a huge distorted pentagon between Scorpius to the south and Hercules to the north. Dominated by second magnitude Rasalhague (Alpha Ophiuchi), the eastern portion of it is host to the western branch of the Milky Way. To the northeast in the giant constellation is a small, pretty vee- shaped asterism called "Poniatowski's Bull," which at one time was considered a constellation in its own right.
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