Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. A high cloud throws yet more
glorious shadows into the daytime sky.
Astronomy news for the week starting Friday, August 29, 2003.
The Moon moves through its waxing crescent
phase the first part of the week, and reaches its
first quarter, where it is 90 degrees to the east of the Sun,
on Wednesday, September 3, well before Moonrise in the Americas.
With the Sun slowly nearing the autumnal equinox in Virgo, the quarter Moon is nearing
the winter solstice in Sagittarius, and will be quite low in
the sky for mid-northern latitudes, rising in the southeast after
noon and setting in the southwest before midnight. The next first
quarter, on October 2, will be slightly more southerly yet.
Following last week's Mars
Madness, we now have little Pluto,
far out of sight to the naked eye, ceasing its retrograde motion well to the north of the ecliptic in Ophiuchus.
Mars of course, despite having passed opposition to the Sun,
is still glorious
within southern Aquarius, as
September begins rising just a hair after sunset and crossing the
meridian to the south at local midnight (about 1 AM Daylight Time).
The most earthlike of all other planets, Mars has a rotation period just slightly greater than that of
Earth, and an obliquity to its ecliptic very similar to ours,
resulting in similar seasons, just twice as long, since it takes
the planet (half again as far from the Sun as we are) 1.9 Earth-
years to make a full circuit of the Sun. Under the summer zenith
Sun, the temperature of the thin Martian air (which is mostly
carbon dioxide with a little nitrogen thrown in) can hit the
freezing point of water.
The only other planet available for viewing is
Saturn, which, now rising just before 2 AM, will shortly be
making an impact on the night sky. Taking 29.5 years to orbit the
Sun, the ringed planet (glorious in even a small telescope) moves
slowly against the stellar background, on the average taking some
two years to traverse a zodiacal constellation. Having spent the
last viewing season wandering through eastern Taurus, Saturn is now beautifully
set within the confines of Gemini.
Evening viewing finds the summer stars at their best. Look for the
Summer Triangle of Vega, Deneb, and Altair, respectively in Lyra, Cygnus, and Aquila,
and if under a dark sky admire the Milky Way
plunging down through Cygnus into Sagittarius, which for mid-
northerners lies low in the south around 9 PM, the handle of its
famed asterism, the upside-down "Little Milk Dipper," sticking into
the Milky Stream. From mid-southern latitudes, South America and
Australia, Sagittarius and the center of the Galaxy shine
gloriously overhead.
