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Astronomy Picture of the Day


Photo of the Week.. The brilliant Sun illuminates a river of flowing clouds (the third in a set of five panoramic cloudscapes).

Astronomy news for the week starting Friday, July 5, 2002.

Phone: (217) 333-8789
Prepared by Jim Kaler.

If you like stars, go to STARS: Portraits of Stars and their Constellations, compiled from previous stars of the week. Access Skylights' Archive, now available from January 4, 2002, to the present. Enjoy photographs of the January 20, 2000 total eclipse of the Moon. Watch planets move against the background stars. See sunsets, rainbows, the Moon and planets, and other sky phenomena in Sunlight.

The Moon wanes through its late crescent phase this week, descending closer and closer to the eastern morning horizon. It finally passes new the morning of Wednesday, July 10. Look the morning of Sunday the 7th to see the thinning lunar crescent passing just above Aldebaran and the Hyades in Taurus, and then again the following morning to see the Moon passing just to the north of Saturn, which is now clearing morning twilight. Though the Moon will be in its waxing crescent phase the night of Wednesday the 10th, the crescent will be too thin to see. We will have a much better view the following night, on Thursday the 11th, as the crescent -- its nighttime side awash with earthlight -- begins to climbs the western evening sky.

Planets, which dominated the scene just a little while ago, are now hard to find. The exception is Venus, which, glowing brilliantly in western twilight, is each night a bit farther to the east of the Sun and at the same time growing a little brighter. The morning of Wednesday the 10th, Venus passes north of Regulus in Leo, so the evening of Tuesday the 9th you will find the planet a bit to the northwest of the star, the night of Wednesday the 10th, a bit to the northeast.

The week again belongs to our Earth. Following in the wake of the passage of the summer solstice, the Earth passes its orbital aphelion point, where it is farthest from the Sun (94.5 million miles, 152 million kilometers, 1.4 percent farther than average), the night of Friday, July 5, at 11 PM Central Daylight Time (midnight EDT, 9 PM PDT). Since the Earth is farthest from the Sun during the heat of Northern Hemisphere summer, it is obvious that the seasons have nothing to do with the distance between us and the Sun, but rather with the tilt of the Earth's axis, which brings the Sun much more toward the overhead point in summer than it does in winter.

The summer constellations are finally making headway into the evening sky. By 11 PM, a great stack of constellations stands to the south for northern hemisphere observers. Close to overhead is the hero Hercules. Just to the south lies the dimmer, but equally great, constellation Ophiuchus, the Serpent Bearer. Ophiuchus, symbolized in the stars by a giant distorted pentagon, appears in mythology to be wrapped by the giant snake, Serpens, the pair of interlocked constellations the forerunner of the caduceus, the physician's symbol. Serpens is the only constellation to come in two parts, the head, Serpens Caput to the west of Ophiuchus, Serpens Cauda to the east. Below the pair, Scorpius, the Scorpion, hovers above the southern horizon.

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