Astronomy news for the two weeks starting Friday, December 21,
2012.
Best wishes to all for a fine holiday season, a good year in 2013,
and clear skies. The next Skylights will appear January 4,
2013.
The Moon starts off our fortnight just past its first quarter, so leads with its waxing gibbous phase, which ends at full Moon the morning of Friday, December 28,
about the time of Moonset in North America. Our second week is
then spent admiring the waning gibbous
phase, which endures until third quarter
arrives the night of Friday, January 4. The big event is another
close passage between the bright Moon and Jupiter on
Christmas night, the Moon (coincidentally at its apogee) climbing the sky
with Jupiter on top (the Moon actually occulting the bright planet
as seen from parts of South America and Africa). The previous
evening, look for Jupiter to make a neat triangle with the Moon and
the Pleiades: providing you
can make them out in bright moonlight.
With us nearly all night, Jupiter dominates the sky, appearing high
to the south in the hours before midnight, and by the end of our
period still not setting until after 4:30 AM well in the northwest.
In the morning, while Saturn enters
more and more into the scene (at the New Year rising in dim western
Libra around 2:30 AM), Venus (though as
always still very bright) crosses a bit of a line, as at year's end
it rises just as twilight begins to light the sky. In the last of
planetary news, Pluto (once the
"last planet") ends the year in near-conjunction with the Sun.
The fortnight begins with the Sun at the Winter Solstice in Sagittarius, which announces the start of astronomical
winter, giving us the shortest day and longest night. Then around
midnight on New Year's Day (as the first goes to the second), the
Earth passes perihelion, where it is closest to the Sun, 1.7
percent closer than the average of 149.6 million kilometers (92.96
million miles), obviously showing that solar distance has nothing
to do with the seasons (which
are caused by the 23.4 degree tilt of the rotational axis against
the orbital perpendicular). Finally, one of the better meteor
showers of the year, the
Quadrantids (named after a defunct constellation near the handle of the
Big Dipper), peaks the night of
Wednesday the 2nd (morning of the 3rd), but will be marred by a
bright Moon.
In mid-evening, look for the roundish head of Cetus, the Whale or Sea Monster,
about half way up the sky, his body floating off to the west. If
you can't find it (once the Moon is out of the way), the vee-shaped
head of Taurus, the Bull (just
to the south of Jupiter), points right at it.
