Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9


Photo of the Week. Wind-blown clouds adrift in a blue sea.

Astronomy news for the week starting Friday, September 3, 2010.

The Moon goes through its new phase this week on Wednesday, September 8, its absence from the nighttime sky allowing us a fine view of the stars. During most of the week we see the Moon fade away in its waning crescent, with the last reasonable view in eastern morning twilight being on Monday the 6th. We then do not pick it up again until the evening of Thursday the 9th as an ultra-thin waxing crescent in western evening twilight. That same day, the crescent passes several degrees south of Saturn, the event effectively invisible. Better to wait until the following evening to spot our lunar companion. Six hours before new, the Moon passes perigee, where it is closest to the Earth, pairing of the two bringing especially high and low tides to the coasts.

The evening planetary sky is but a ghost of what it has been. Saturn is now lost to evening twilight and Mars, while still more or less visible, has much faded as it passes two degrees north of Spica in Virgo on Saturday the 4th, the first magnitude star 60 percent brighter than the planet, which has slipped to bright second magnitude. Venus, however, remains in charge of evening twilight (Mars up and to the right of it). Low in the sky, the planet continues to brighten some as it approaches Earth. After reaching maximum brilliance in late September, it will rapidly exit the evening, only to pop up in November's morning sky. A telescope shows a crescent, as the daytime side is obviously facing the Sun, with mostly nighttime then facing Earth.

As Venus sets at the end of twilight (around 9 PM Daylight Time), Jupiter then rises in the east. Pulling an all-nighter, it transits the meridian to the south about 2 AM. Look for it to the southwest in morning twilight, which is rapidly getting later and later as the Sun moves to the south along its ecliptic path.

If you are lucky enough to find a dark location, with the Moon out of the way, this is a fine time to admire the Milky Way as it cascades from the north through Cygnus and Deneb down through Aquila and Altair. It brightens to the south through modern Scutum and then hits its peak in Sagittarius, where it is sadly dimmed for northerners by the Earth's thickening atmosphere. To the east of Cygnus, we see the rising of that harbinger of Fall, the Great Square of Pegasus, as Cassiopeia climbs the northeastern sky.
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