Astronomy news for the week starting Friday, December 25, 2009.
Wishes for a fine holiday season to all.
The Moon
cooperates in the celebrations by taking the last week of the year
to go through its entire waxing gibbous
phase, beginning with first quarter on
Thursday, December 24, Christmas Eve, and culminating on Thursday,
December 31, New Year's Eve, with its full
phase.
A variety of lunar events and effects enhance the affair. First,
this full Moon -- the Cold Moon, the Long Night Moon -- is the
second one for the month of December, the first having taken place
the night of December 1. Since the first one already has a
traditional name, this one is by more-or-less recent folk tradition
called a "blue moon." Its color, however, will be the usual silver
white (or reddish if rising).
Second, the Moon highlights the end of the year by being partially
eclipsed
by the shadow of the Earth. Unfortunately, full Moon takes place
during mid-day in North America, with the Moon quite out of sight,
so it's a European, African, and Asian affair. But don't feel
sorry for ourselves, as it is not much of an eclipse, the south
pole of the Moon just barely ticking the dark terrestrial umbra.
Those on the other side of the world won't see much either.
Then, with the Sun
still very close to the Winter
Solstice in Sagittarius, the
full Moon -- opposite the Sun -- will be just to the east of the Summer Solstice in classical Gemini (never mind that the Earth's
precessional wobble has taken the
Solstice across the "official" border into Taurus). This full Moon will therefore be the highest
of the year, at least as seen from the mid-northern hemisphere, as
it will more or less replicate the behavior of the Sun on the first
day of summer (perhaps making us feel warmer).
Enough of the Moon; on to the planets! While slipping away to the
west,
Jupiter remains nicely visible in early evening, dropping to
the horizon to set around 8:30 PM. Earlier, you might catch a
glimpse of
Mercury in southwestern twilight. Mars,
still rising just before Jupiter disappears, continues to brighten
in western Leo, the two planets
nearly opposite one another. Saturn
then passes a bit of a milestone by rising around midnight in
western Virgo, as it becomes an
evening object. Our planetary year then finally ends with Pluto
going through conjunction with the Sun on Christmas Eve, making it
doubly invisible.
Early evening is about your last chance to see Fomalhaut to the southeast of
Jupiter. But to the northeast of the giant planet, the Andromeda gang still hangs
around. In particular it's a wonderful season for the star-streams
of Perseus, who rides high, nearly
overhead, in mid-to-late evening.
