Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Winds aloft blow streaming
horsetails from high cirrus clouds set before a stunning blue sky.
Astronomy news for the two week period starting Friday,
September 12, 2003.
Skylights is also presented a day early, and will return on
Saturday, September 27.
During this extended period, the Moon passes two phases "of the moment."
Beginning in its waning gibbous phase, it passes third
quarter on Thursday, the 18th, about the time of Moonset in
North America. Near the Summer
Solstice, and at the same time swinging north of the ecliptic
on its tilted orbit, this third quarter will be the highest of the
year, our companion nicely set in eastern Taurus. Waning through crescent, the Moon will then
pass its new phase on Thursday, the 25th.
As the Moon orbits, it will pass north of Saturn
the night of Friday the 19th (shortly before Saturn rises,
which it does around local midnight, 1 AM Daylight Time) and then
north of Jupiter
the night of Tuesday, the 23rd, again before the planet rises. The
morning of the 20th, the Moon will reside to the northeast of
Saturn. The morning of the 23rd find the thinning crescent
beautifully placed in twilight in Leo above rising Jupiter. The morning of Wednesday,
the 24th, the even thinner crescent will be situated more or less
between Jupiter and Mercury, the latter making a very nice appearance
for us. The little planet will reach its greatest western
elongation on Friday, the 26th, when it is 18 degrees to the west
of the rising Sun.
Of all the planets,
Mars of course still dominates, as it shines brilliantly among
the faint stars of Aquarius. Look
directly below the red planet as it climbs the southeastern sky in
early evening to find the star Fomalhaut in Pisces Austrinus, the "Southern Fish."
However, it is planet Earth that makes the biggest
splash. At 5:47 AM Central Daylight Time (6:47 Eastern, 3:47
Pacific), the Sun will pass
the autumnal equinox in Virgo.
Astronomical fall will then commence in the northern hemisphere,
spring in the southern. At that moment, the Earth's axis will be
perpendicular to the line to the Sun, the Sun will be on the
celestial equator, will rise due east, set due west, be up for 12
hours, and down for the same. (The extended solar disk and
refraction by the Earth's
atmosphere, which raises the Sun somewhat from its real
position, actually causes the day to be a few minutes longer than
the night). People at the Earth's equator will see the Sun pass
through the zenith (the overhead point). The Sun also formally
sets at the north
pole, and finally rises at the south
pole (though again solar diameter and refraction make the Sun
linger a bit at the north pole, and rise a bit early at the south).
With autumn making its debut, the summer constellations are near
the meridian at sunset (admire Sagittarius now and its Little Milk Dipper while you
have the chance), and the fall constellations make their bid for
attention. Watch the rising of the Great Square of Pegasus, and see the "W" of Cassiopeia climb the northeastern sky.
