Skylights featured five times on Earth Science
Picture of the Day: 1
Photo of the Week. A very thin waning crescent Moon
reveals its nighttime side eerily awash with light from a nearly
full Earth. The irregularities in the bright lunar daytime edges
are real, and are caused by crater rims catching the last rays of
sunlight. The dark areas, which in full Moonlight make the "man in
the Moon," are giant impact basins. The large ghostly crater at
far right is Tycho. Photo by Mark Killion.
Astronomy news for the week starting Friday, December 23, 2005.
Welcome to the last full week of the year, with wishes to everyone
for a good holiday season. The week begins on Friday, December
23rd, with the third
quarter Moon and proceeds with the Moon running through its waning crescent phase almost to new,
which it will pass next Friday, the 30th.
As the Moon goes along to the east against the stellar background,
it makes a bunch of passages. On Christmas morning before dawn,
the Moon will be seen approaching Spica in Virgo, and actually occulting it for those in western
North America (where it is dark, around 6 AM PST). The Moon next
takes on Jupiter, passing a few degrees to the
south of the giant planet shortly before it rises on the morning of
Tuesday the 27th. The next morning watch for it just below bright
Dschubba, Delta Scorpii, and up
and to the right of Antares,
which it will occult for as seen from the eastern hemisphere.
Finally, the morning of Thursday the 29th, the Moon will rise just
before dawn as a very slim and pretty crescent (see the above
photo). As it proceeds, watch for Earthlight to grow on the
As the year approaches its end, Venus is quickly slipping away. At week's
end, it sets just as twilight fades. Its place is taken by Saturn and Sirius, which rise just a bit later,
about 7:30 PM, half an hour before bright reddish Mars (still in
Aries) crosses the meridian to
the south. Wait then until 3 AM when Saturn takes its turn at the
meridian, half an hour after which Mars sets and Jupiter rises, all
in a lovely symmetric dance.
In early evening look high, close to overhead, for streams of stars
that make the maiden Andromeda, who is perpetually poised to be rescued by
Perseus to her east. The
westernmost star of the constellation, Alpheratz (Alpha Andromedae)
serves also as the northeastern corner of the Great Square of Pegasus, the famed asterism of
Pegasus, the flying horse on
which Perseus forever rides. South of the southern curve of
Andromeda, look for two stellar triangles, the northern one Triangulum (the eponymous Triangle),
the southern the main figure that makes Aries, the Ram, the
constellation of the Zodiac that
held the Vernal Equinox in ancient
times (because of precession, the 26,000 year wobble of the Earth's
axis, that job now taken over by Pisces).