Skylights featured on Astronomy Picture of the Day

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

Thunderstorm cell

Photo of the Week.. Continuing the "thunderstorm series": inside a small but turbulent thunderstorm cell, the occluded sky is made orange by the setting Sun. Compare with a nearby cell and its more distant view.

Astronomy news for the week starting Friday, July 12, 2005.

The Moon starts our week in its first quarter, the phase reached just after sunset the night of Friday, August 12, giving us in North America a nice view of the precise quartering of the orbit, half the lunar disk illuminated, the other half in night. The dividing line between night and day, the "terminator," will thereafter slowly sweep across the waxing gibbous Moon, bringing daylight to more and more of the side of the Moon that faces the Earth. Since the Sun is slowly moving toward the autumnal equinox, the Moon -- moving ahead of the Sun -- plunges far to the south. The night of Saturday the 13th finds our neighbor to the west of Antares of Scorpius, while the night of Sunday the 14th sees the reverse, the Moon now to the east of the red supergiant. (The Moon will occult the star as seen from the Earth's eastern hemisphere.) Around midnight the night of Thursday the 18th, the Moon passes perigee, the point at which it is closest to the Earth (a bit over five percent closer than average), only half a day before its full phase, which takes place around noon on Friday the 19th. The nearly-full perigee Moon will therefore rise just before sunset the night of Thursday the 18th. Earlier that day, the Moon passes south of Neptune in Capricornus.

The Moon aside, the showstoppers are now Jupiter and Venus, which dominate the western evening sky as they head toward conjunction on September 2, giving us a fine view of the two brightest planets of the sky. (Under ideal circumstances, Mars can just barely top Jupiter, though it is far from doing so now.) While Venus sets just before the ending of evening twilight, Jupiter sets shortly after, around 10 PM Daylight Time, so you have to admire the pair early. Watch next for the rising of Mars almost exactly an hour later.

Be on the watch early in the week for continuing Perseid meteors, which will still be at their best the morning of Saturday the 13th, the meteors the debris of Comet Swift-Tuttle. With no Moon in the early morning sky, if in a dark location, you could see up to one a minute seeming to radiate from the constellation Perseus.

Can you find the two celestial crowns? Look to the east of Bootes (marked in western evening by bright orange Arcturus) to find the small semicircle of Corona Borealis, the Northern Crown. Close to the southern horizon, below the Little Milk Dipper of Sagittarius, lies a similar figure, Corona Australis, the Southern Crown. Just east of the richest part of the Milky Way, Corona Australis is rich in stars in the process of their formation.
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