Photo of the Week.. Clouds throw spectacular shadows
into bright air.
Astronomy news for the short week starting Friday, December 6,
2002.
The Moon, having passed its new phase last week, waxes through its
crescent phase the early part of this week, and reaches its first
quarter, when we see half the lunar daytime and half the lunar
nighttime sides, on Wednesday, December 11. Look to the west in
twilight for the slim crescent, the nighttime side of the Moon
glowing with light reflected from
the Earth, the night of Friday the 6th. While the shortest day of
the year takes place when the Earth passes the Winter Solstice in Sagittarius (this year on December 21), the earliest sunset and
evening twilight occur some two weeks earlier, during the two-
week period centered on December 7, the result of the eccentricity
of the Earth's orbit and the 23.5 degree tilt of its axis. By the
time of the Solstice passage, the evening drive home after work is
noticeably brighter.
We begin the week with
Venus glowing at its very brightest in its current morning
appearance. As it climbs yet a bit higher in the sky, the planet
will dim some, but the fading will be so little for now that it
will be hardly noticeable. Venus is making an extended month-long
visit with much dimmer reddish
Mars, which lies nearby, just to the west. Though Venus
quickly approached Mars, both are now moving to the east against
the starry background, and Venus is moving the faster, so the two
do not come into actual conjunction. Closest approach, when they
are only 1.5 degrees apart (three times the angular diameter of the
Moon), takes place on Friday, the 6th.
By contrast with the morning sky, which contains the two planets
that flank the Sun, the evening sky is now graced with the two
giants of the Solar System, Jupiter and Saturn, the ringed planet rising just after sundown, Jupiter
just after 9 PM. Far beyond them, the three outer planets make a
"hidden" appearance, as the crescent Moon passes 5 degrees north of
Neptune on Sunday the 8th, and the same angle north of Uranus just over a day later, both planets in direct easterly
motion in Capricornus, Uranus close
to the Aquarius border. In supreme
invisibility,
Pluto then passes conjunction with the Sun on Monday, the
9th.
Andromeda and Cassiopeia take center stage in early
evening, the famed "W" of the celestial Queen high overhead for
those in mid-northern latitudes, Andromeda due south. People in
the southern tropics would see Cassiopeia swinging just above the
northern horizon, while those in mid-southern latitudes would see
brilliant blue Achernar, the
star at the end of the River Eridanus, over their heads, Achernar quite invisible
from most of the US and all of Canada. Between the two lies the
celestial equator, which in early evening is embraced by the
fainter figures of Pisces and
Aquarius. Crossing the meridian to the south in early evening is
the Vernal Equinox, the point
passed by the Sun on the first day of spring, the Equinox just down
and to the left of Pisces' obvious (if one has a dark sky) "Circlet."
