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

Meteor Crater

Photo of the Week. The famed Barringer Crater ("Meteor Crater") near Winslow Arizona (USA) is an impact site three-quarters of a mile across and 600 feet deep, made 50,000 years ago by a house-sized nickel-iron asteroid. As big as it is, it pales beside others like Manicouagan. (See it at full resolution.)

Astronomy news for the week starting Friday, September 8, 2006.

The sky is quiet this week as summer draws toward its end. The Moon is now running through the back half of its journey around the Earth. Spending the week in the waning gibbous phase, it passes through third quarter at week's end on Thursday the 14th. With the Sun approaching the autumnal equinox in Virgo, the third quarter, 270 degrees around the orbit from new, will be high along the ecliptic approaching the summer solstice in Gemini/Taurus. Watch for it making a fine appearance above Orion, which even though it is still summer is giving us a glimpse of the coming winter. The Moon begins the week near perigee, where it is closest to the Earth.

As the seasons change (though autumn does not formally begin until September 22), it hardly seems possible that summer is actually three or so days longer than winter (and spring longer than fall). The origin for this "inequality of the seasons" (known since ancient times) is the eccentricity of the Earth's orbit. We are closest to the Sun in early winter, which causes the Earth to move faster in orbit and thereby to hustle through the colder months. Southern hemisphere residents see the opposite effect.

Jupiter (in Libra) still dominates evening, though not by much. Look for the giant planet in the southwest in late twilight. By 9:30 or so, it is gone, leaving the evening sky planetless except for the three faint outer ones: Uranus (in Aquarius), Neptune (in Capricornus), and Pluto (near the Ophiuchus-Serpens-Sagittarius boundary). News has it that the planetary research community is not at all happy with the International Astronomical Union's decision to send Pluto to the minors, so for now let's keep it as a real planet. The morning sky is still graced by Venus, but again not by much, since the bright "morning star" does not rise until mid- twilight, around 5:30 AM. Saturn, however, now rises around 4 AM, well before dawn's onset. Moving eastward, the ringed planet is now passing from Cancer into Leo.

The early evening sky still contains one the grandest of constellations, Scorpius, which dips very low to the southern horizon. Look for Antares -- Alpha Scorpii -- rather well to the left of Jupiter. Above Scorpius is a stack of large constellations that begins with Ophiuchus, then goes through Hercules and Draco, finally ending at Polaris.
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