SKYLIGHTS
Astronomy news for the week starting Friday, August 31, 2001.
Precious little actually "happens" this week. The Moon brightens
and heads to full, the phase reached early, the night of Sunday,
September 2. Almost exactly one day before technical "fullness,"
the Moon also passes its apogee point at a distance of 406,330
kilometers (252,480 miles) from the Earth, the maximum distance
minimizing high ocean tides. As autumn comes on, the full Moons
fall farther to the north, this one near the Aquarius-Pisces
border. Traditionally, the September full Moon is called the
"Harvest Moon." The ecliptic, the apparent path of the Sun, is in
the evening near its flattest to the horizon, and as a result the
delay in moonrise is at a minimum, the effect flooding the fields
with bright moonlight after sundown. The October full Moon, the
"Hunter's Moon," actually fills the bill better, as this year it
occurs quite a bit closer to the beginning of fall on September 22,
when the Sun will cross the autumnal equinox.
In spite of the week's quietness, the sky still keeps on turning,
stars and planets rising and setting daily and shifting to the west
an extra degree every day as the Earth goes around the Sun. In the
evening, bright Mars hangs to the south-southwest after dark, while
Saturn (much fainter, but still brighter than any star of the
northern hemisphere) begins to make its move into the evening sky,
now rising just before midnight daylight time. About an hour and
a half later, bright Jupiter (which has pulled well the west of
Venus) lofts itself over the northeastern horizon; Venus saves
itself for around 4 AM, rising just over an hour before morning
twilight commences.
Though bright moonlight floods the nightly scene early in the week,
you can still admire the glorious Summer Triangle, which consists
of Vega (in Lyra), now high in the sky for northerners as night
falls, Deneb (in Cygnus) to the east of Vega, and Altair (in
Aquila) to the south of the pair. When the Moon finally disappears
from early evening, if you live in a dark site you can see the
Milky Way flooding southward through the Triangle. As the Milky
Way leaves Aquila, it brightens through the modern constellation
Scutum (the Shield), and then even more so through Sagittarius, the
Archer, whose arrow points toward the center of the Galaxy. In the
other direction, the Milky Way flows from Cygnus into the coming
autumn constellations, through Cassiopeia and then into Perseus.
Already the flying horse of the Perseus myth, Pegasus and its Great
Square, are climbing the eastern sky in late evening. There are
only three weeks to go until the beginning of autumn in the
northern hemisphere, spring in the southern.
