SKYLIGHTS
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.
