Astronomy news for the week starting Friday, December 4, 2009.
Skylights now resumes its normal weekly schedule.
The Moon is
making its late rounds this week. Having passed full at the beginning of the month, it
starts us off in its waning gibbous phase
as it heads towards third quarter, which
takes place the night of Tuesday, December 8, before Moonrise in
North America. Though the same amount of the Moon is visible at
first quarter as at third, the third is only half as bright as the
first as a result of its having more dark maria, or lava flows, upon it. The Moon then
spends the remainder of the week in the waning crescent, which thins as morning-to-
morning it descends to the eastern horizon.
As our lunar companion treads its path, it will appear to the west
of Mars the
night of Saturday the 5th, and will then pass nicely to the south
of the red planet (the reddish color coming from iron oxides in the
surface "soil") the night of Sunday the 6th. A few days later, on
the morning of Thursday the 10th, the Moon will then pass well to
the south of Saturn.
Jupiter makes
something of a transition this week as it crosses the meridian at sunset and thus appears to
the west of the north-south line when it becomes visible at dusk.
It then sets early, just after 9:30 PM. Half an hour before,
however, Mars rises (its rising time getting rapidly earlier), and
then transits the meridian an hour before dawn begins to light the
sky. Then we stay in the morning skies with the rising of Saturn
around 1 AM. The sight at 5 AM is glorious, with
Castor and Pollux, Mars,
Regulus, Saturn, and
Spica all in a row cascading from
northwest to southeast along the
ecliptic.
The inner planets, however, are effectively gone from
us. In the morning, Venus now rises
just half an hour before sunrise, and in the evening, Mercury, while
climbing slowly out of dusk, is not yet high enough to see.
It's the Sun itself that makes a bit of a splash. As a result of the
eccentricity of the Earth's orbit and the tilt of the rotation axis,
the earliest sunset takes place on December 7, two weeks before the shortest day.
Watch then as the evenings begin to get lighter.
The Sea Monster is upon us. Follow the left side of the Great Square of Pegasus downward to rather bright
Deneb Kaitos, Beta Ceti, the
tail of Cetus the Whale. The
rest of the constellation spreads
up and to the left (to the left of southern Pisces) to the ragged circle of stars that marks the
Monster's head. Along the way lies Mira, "the Wonderful," one of the
classic variables of the sky. Can't find Cetus? Wait for the
rising of more obvious Taurus.
The Bull's vee-shaped head points directly at the Whale's head,
each of the two beasts seen as rather contemplating what the other
one is all about.
