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Astronomy Picture of the Day


Photo of the Week.. Puffy fair-weather clouds float in a brillinat blue sky (the fourth in a series of five panoramic cloudscapes).

Astronomy news for the week starting Friday, July 12, 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. 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 grows through its waxing crescent phase the early part of the week, reaching its first quarter about the time of moonset in the Americas the night of Tuesday the 16th. Three days before, it passes perigee, where it is closest to the Earth.

The climbing crescent will play games with Leo and Venus. The evening of Friday the 12th, in western evening twilight the Moon, its full disk lit with Earthlight, will be down and to the right of the star Regulus and Venus, while the night of Saturday the 13th, the Moon will be up and to the left of them. Venus, brilliantly lit by the Sun, will itself be just up and to the left of the star. On the night of the first quarter, Tuesday the 16th, the Moon will lie just north of the next first magnitude star of the Zodiac, Spica in Virgo, while the following night finds it smack in the middle of dim Libra. Both Regulus and Spica are regularly occulted, or covered, by the Moon as it circuits Earth, but not this time, as the Moon, in its tilted orbit, is passing to the north of both of them.

The other planets are pretty much out of sight. Mars and Jupiter pair together low in the west in evening twilight to the east of the Sun, while Mercury and Saturn pair to the west of the Sun in the eastern sky in morning twilight. Much fainter Uranus and Neptune pair far to the south, Uranus just barely over the line into western Aquarius, Neptune still hanging out in Capricornus, where it will be for many years to come. Pluto, odd man out, sits in southern Ophiuchus.

The glorious summer sky is now coming into easy evening view. By 10 PM, just as the last glimmers of twilight have ended, great Scorpius lies directly to the south with first magnitude Antares at its heart, the scorpion's curved tail grazing the southern horizon for those in middle northerly latitudes, Scorpius defies the standard statement that a constellation's stars are just randomly distributed. The figure is filled with massive blue-white stars that belong to different "associations", in which all the stars were born at more or less the same time and stay together for most of their lives. Antares, though now a swollen and dying red supergiant, used to be one of them. This concentration of luminous stars gives Scorpius its character and sparkle. In the winter sky, Orion is created in much the same way, as is Perseus in autumn. We find these associations spread out along the Milky Way (where stars are born), which later in the night will be seen cascading high out of Cygnus, then down through Sagittarius and the wonder of Scorpius.

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