SKYLIGHTS
Astronomy news for the week starting Friday, November 17, 2000.
The week begins with the Moon a day shy of third quarter, the phase
reached on Saturday, the 18th, in mid-morning in North America,
when the Moon can still be seen to the west in the daytime sky.
Before the Sun brightens the sky Saturday morning, the near-third-
quarter will be just to the west of the Sickle of Leo and the first
magnitude star Regulus. As it wanes through crescent, the Moon
will appear just to the west of Mars the morning of Tuesday, the
21st, allowing one to locate the red planet, which because of its
distance is still (at second magnitude) not all that
bright.
The real planetary news concerns Saturn, which passes opposition
with the Sun on Sunday the 19th against the stars of western
Taurus. At that time, Saturn will have its maximum retrograde, or
backward (westerly), motion against the stellar background, will
rise at sunset, and set at sunrise. Jupiter, to the east of Saturn
(and rising brilliantly shortly after sundown), will follow suit
next week. Retrograde is merely a consequence of the speedier
Earth passing in between an outer planet and making it look as if
it is going in the reverse direction. The Saturnian opposition
highlights some cultural heritage, the three days centered on
Sunday named after celestial figures, "Saturday," "Sunday," and
"Monday" the days of Saturn, the Sun, and the Moon (the other days
of the week, in English, reflecting Norse gods).
The morning and evening skies are respective hosts to the two
inferior planets, Mercury and Venus (the name reflecting their
positions interior to the Earth's orbit). Mercury passed its
maximum angular separation from the Sun last week and, though still
visible, is now daily getting closer to the horizon in morning
twilight. Venus, on the other hand, now brilliant in the southwest
in evening twilight, is climbing higher and higher, its maximum
separation not achieved until we are well into the year 2001.
Through the telescope, each planet looks similar however, rather
like an out-of-round gibbous Moon.
The mid-evening hours now play host to the highest arch of the
Milky Way. The Milky Way, the combined light from the billions of
stars of the disk of our Galaxy, is tilted at a 63 degree angle
relative to the celestial equator (the plane of the Earth's
rotation). The Milky Way's most northerly position lies 63 degrees
north of the equator, just north of Gamma Cassiopeiae, the central
star of the "W" of Cassiopeia. The most southerly (and very
bright) portion of the Milky Way, on the other hand, falls 63
degrees south of the equator, just to the south of the glorious
Southern Cross, which does not rise for anyone north of 27 degrees
north latitude.
