Skylights featured five times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
, 5
Photo of the Week. Clouds throw their shadows toward
the ground below.
Astronomy news for the week starting Friday, October 28, 2005.
We begin the week with the Moon in its
waning crescent phase, each morning
becoming closer to the horizon and more into dawn. Always with us,
it will then just SEEM to disappear for awhile as it goes through
its
new phase, passing more or less between us and the Sun (missing
it, so no eclipse) on Tuesday, November 1. It will thereafter
become visible as a slim waxing
crescent in bright western twilight the night of Thursday the
3rd. Watch as the growing crescent moves out of the evening's glow
and also partners both the inner planets,
Mercury and
Venus.
In a very unusual coincidence, these two planets reach their
greatest eastern elongations almost simultaneously, within three
hours of each other, on Thursday November 3. (At greatest eastern
elongation, they are farthest in angle to the east of the Sun and therefore near
best visibility at night; at greatest western elongation, they are
best visible in the morning.) On that date, Venus will be 47
degrees to the east of the Sun, while Mercury will be
24 degrees to the east. The low angle of the evening ecliptic to the horizon,
however, makes the planets rather hug the ground. While Venus is
eminently visible in the early evening (the brightest thing in the
sky other than the Moon), Mercury's visibility is severely
compromised by low altitude for those of us in the northern
hemisphere. Because the evening ecliptic will be coming back
upward, Venus will oddly seem to climb in the sky farther out of
twilight in spite of getting closer in angle to the Sun, setting
later and later until late November. It will also keep getting
brighter until December 9, when it peaks. Now add the Moon. The
night of Thursday, November 3, the thin crescent will lie just
below Mercury, making it possible to find the little planet -- use
binoculars. Two nights later, on Saturday the 5th, the waxing
crescent will lie just to the left of Venus in a near-classic
pairing.
As the sky darkens, you can then look to the east to see very
bright Mars (now
in southeastern Aries to the
north of the head of Cetus).
Continuing the planetary coincidences, Mars is closest to Earth in
its current round of visibility (70 million kilometers, 43 million
miles), and therefore brightest, on Saturday October 29th. It will
pass opposition to the Sun, when it rises at sunset and sets at
sunrise, on Monday, November 7. (The two dates do not coincide
because of the eccentricity of the Martian orbit.) Later in the
evening, watch for the rising of Saturn at
midnight daylight time, the ringed planet ensconced in Cancer just southeast of the Beehive Cluster.
The stars of the Andromeda
myth are now on wonderful display in mid-evening, the gang of six
constellations led to the west by rather dim Cepheus, the King, whose Queen,
famed W-shaped Cassiopeia, is seen
rising high in the northeast. Cepheus himself
forms a much fainter pentagon whose best-known resident Delta Cephei, the prototype of the
Cepheid variables
that provide us with a measuring stick with which to establish the
distance scale of the Universe.
