Photo of the Week. Now it's Halley's Comet as it
appeared in early March of 1986. See full
resolution. University of Illinois and San Diego State
University, courtesy of Ron Angione.
Astronomy news for the two weeks starting Friday, December 6
The next Skylights will appear Friday, December 20, 2013.
We begin the week with the Moon in its waxing
crescent phase as it heads towards first
quarter, which is passed on Monday, December 9, shortly before
it rises in North America. As it rounds the Earth it then moves
into the waxing gibbous, which ends with
full Moon on Tuesday the 17th. During the
remainder of the fortnight, the Moon fades in the waning gibbous phase. The evening of Friday
the 6th, look for the waxing crescent well up and a bit to the left
Venus. The night of Saturday the 14th, the rising Moon will
shine to the right of the Pleiades, while the next evening finds it smack in the
Hyades of Taurus, with Aldebaran below it. The full Moon
Jupiter, seen rising well to the west of it the night of
Tuesday the 17th, then just to the south the following night. The
Moon passes apogee, farthest
from Earth, on Thursday the 19th. Of more interest, because of the
Earth's orbital eccentricity and axial tilt, we see the earliest
sunset of the year on Saturday the 7th in spite of Winter Solstice passage not taking
place until Friday the 21st.
Venus and Jupiter dominate the early evening, though Venus is
starting to slip away. Reaching its greatest brilliance on Friday
the 6th, the planet does not set in the southwest until an hour
after the sky gets fully dark. By that time, Jupiter is well up in
the northeast and quite unmistakable near the star Delta Geminorum
(Wasat) more or less south of Castor and Pollux. Jupiter then crosses the meridian to the south one to two hours
after midnight, getting earlier as the fortnight proceeds. By that
Mars is up in the east as it plods easterly against the
stars of western Virgo, crossing
the celestial equator into the
southern hemisphere on Monday the 16th. Saturn then rises in the
southeast in Libra shortly before
dawn, giving us three planets to admire.
The highlight of the our two-week period (and one of the reasons
for it) is the Geminid
meteor shower, which runs roughly between December 11 and 15 and
peaks the morning of Saturday the 14th, when in a dark sky you
might see more than 100 meteors an hour that seem to come out of
the constellation Gemini.
Unfortunately, the bright gibbous Moon will get in the way. The
Geminids are strange in that they are the debris of the "asteroid"
Phaeton, which behaves more like a comet that takes but
1.4 years to orbit the Sun. Clearly the minor bodies of the Solar
System are more complex than was once thought.