Photo of the Week.. Cloud tops cast spectacular
shadows in a morning sunrise from 35,000 feet.
Astronomy news for the week starting Friday, November 8, 2002.
The
Moonwaxes
in its crescent phase the early part of the week, passing f
irst quarter on Monday, November 11, about the middle of the
afternoon in North America, while the Moon is climbing the daylight
eastern sky. On Saturday, the 10th, the Moon passes well south
(about 5 degrees) of
Neptune, and on the night of Monday, the 11th, equally far
south of
Uranus.
The brightening of the Moon will slowly cause the washing out of
the fainter stars. Curiously, even though they are the same
angular size, the first quarter Moon is roughly twice as bright as
the last quarter. The reason is quickly seen at full Moon even
with the naked eye. The huge, dark, lava-filled impact basins (the
famed "
maria") that make the "Man in the Moon" and other fanciful
creatures, are not evenly distributed, but lie more toward the
Moon's eastern edge (or limb) than toward the western edge. As a
result, they cover more of the lunar territory during third quarter
than they do first quarter, and therefore shed less reflected lunar
light. This uneven distribution extends around to the back, or far,
side of the Moon, where the maria effectively disappear.
Because the Moon rotates on its axis in synchrony with its orbital
revolution, we never get to see the far side; various wobbles allow
us to map about 60 percent of the Moon from the Earth. Our full
knowledge of the far side comes only from spacecraft. Someday
perhaps it will be a home for radio observatories, allowing them to
be entirely free of interference from the Earth.
The innermost planet,
Mercury, is quite out of sight, passing superior conjunction
with the Sun (when it is on the other side of the Sun) on
Wednesday, the 13th. Venus, however, having already passed inferior conjunction
(when it is roughly between us and the Sun), is slowly becoming
visible in the morning sky. By midweek, this closest planet to the
Earth will be rising about the time twilight commences, and will
grace the morning sky ever-more visibly for the rest of the year.
Better, watch also for the ever-earlier rising of Saturn, the ringed planet coming up over the eastern
horizon around 7 PM, with
Jupiter following 4 hours later.
This is the season for Cassiopeia,
Pegasus, and the rest of the gang
from the Andromeda myth.
Look
high to the south around 8 PM to see the large box of stars that
makes the Great Square of
Pegasus. From off its northeast corner swing two graceful
streams of stars that make Andromeda herself. Above the center of
the figure lies the great Andromeda
Nebula, Messier 31, a nearby galaxy much like ours, and at a
distance of two million light years, the farthest thing that can be
seen with the unaided eye. Below Andromeda lies The flat triangle
that makes Triangulum, which is
host
to another, smaller, nearby galaxy, Messier
33, which can also be seen, though just barely, without optical
aid.
