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.Planet Earth: Under a brilliant blue sky, clouds march to the edge of the southern tip of Greenland, the huge island that holds one of the greatest glaciers on Earth. Icebergs float in the North Atlantic just offshore. See full resolution.

Astronomy news for the week starting Friday, October 6, 2006.

The week spans the waning of the gibbous Moon. The full phase, with the Moon opposite the Sun, is passed on Friday, October 6 during the evening hours before midnight in North America. Last quarter is then passed on Friday the 13th.

This is the season of the "Harvest Moon," which is commonly the name of the September full Moon, but since this one is closer to the equinox date, the October full Moon (more commonly called the "Hunter's Moon") serves just as well. Rising nearly due east, the Harvest Moon is caused by the eastern evening ecliptic lying rather flat against the horizon. As a result, the delay in moonrise around the time of full Moon is the smallest of the year, which gives us plenty of early evening post-full-moonlight: just right for the harvests of earlier times.

Jupiter descends even lower into the early evening sky. On Tuesday, October 10, it passes something of a divide, setting as astronomical twilight ends (defined as the time when the Sun reaches 18 degrees below the horizon, and the sky becomes fully dark). So look early to catch the "big guy," as there is little time left before it disappears from the evening altogether. With Mercury making a dreadfully poor appearance in the evening sky, Venus and Mars completely gone to respective morning and evening twilights, that leaves the planetary sky to morning's Saturn. Rising around 2:30 AM Daylight Time in western Leo, the ringed planet stands due east as twilight approaches.

While dominating the planetary sky, Saturn is still no match for the brightest stars. Shining at magnitude 0.5, it is quite overwhelmed by brilliant Sirius (which in the twilight morning sky glows to the south), and also beaten out by Rigel in Orion (up and to the right of Sirius), by Capella in Auriga (north of Orion), and even by Procyon in Canis Minor (to the left of Orion).

Back in the evening, look into the western sky for the trio that makes the Summer Triangle: Deneb in Cygnus (at the top of the Northern Cross), Vega in Lyra (just barely fainter than orange Arcturus, which is escaping to the west), and Altair in Aquila. As autumn deepens, all are reminiscent of warmer days past.
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