Astronomy news for the week starting Friday, July 28, 2000.

The Moon passes its new phase the night of Sunday, July 30, and once again partially eclipses the Sun. And once again, most of us in North America lose out, with the exception of those living in the Pacific Northwest, the western Canadian provinces, and Alaska, who might see up to half the Sun covered. If the circumstances of the lunar orbit are just right, we can have solar eclipses at two successive new moons, as we did in July (the first near the Antarctic, this one in the Arctic). If so, we must have a lunar eclipse in between at full Moon, as we did on July 16. This month is special, as two successive new Moons took place in the same month, allowing us to witness the reversal of the "blue Moon" phenomenon, in which there are two FULL moons in a month.

As new Moon approaches, the slim crescent will appear just above the planet Mercury the morning of Saturday, July 29th, allowing us easily to find the small planet. Look close to the east- northeastern horizon after dawn. The Moon will actually occult Mercury for those in the far northern hemisphere and western Europe. Following its new phase, the Moon will enter its waxing crescent phase, and become visible in evening twilight by the night of Tuesday, August 1. Only a day before new the Moon passes its perigee, the point at which it is closest to the Earth.

No Moon in the nighttime sky means good things for the visibility of the stars and constellations. The advent of August signifies prime Milky Way viewing; if, of course, if you have a dark country sky. At 10 PM, Scorpius and Sagittarius dominate the southern horizon (for those in the upper northern hemisphere), each holding branches of the Milky Way. The divide, called the Great Rift, first appears high to the east in Cygnus. The Great Rift is not an absence of stars, but is caused by a conglomeration of vast dusty interstellar clouds that block the light of the billions of background stars that make the disk of our Galaxy. Within these dusty clouds the temperature falls so low that dense gaseous lumps can condense to form stars. The region directly above Antares in Scorpius (within southern Ophiuchus) is filled with such star forming regions.

While admiring Sagittarius, noted for its famed 5-star upside-down "Little Milk Dipper," note the curve of stars down and to the left, which makes Corona Australis, the Southern Crown, a counterpart to the Corona Borealis, the Northern Crown, which lies high in the sky between Bootes and Hercules.
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