Skylights featured five times on Earth Science
Picture of the Day: 1
Photo of the Week. The Earth's shadow rises in the
evening over the mountains of Arizona.
Astronomy news for the week starting Friday, November 23, 2001.
The Moon, having just come off of its first quarter, expands to
full this week through its waxing gibbous phase, full reached next
Friday, November 30. This makes it a "blue moon" (two full moons
in a month) for Europe and the North American east coast. What
mid-America gained last month, it lost this month, the skies
relentless in averaging it all out. Less than a day after first
quarter, on Friday the 23rd, the Moon goes through apogee, so this
first quarter is about the angularly smallest you will see, though
the difference to the naked eye is hardly sensible.
Saturn, moving toward opposition next week, now rises just after
sunset. Though the planet is the dimmest of the "ancient ones,"
those known since antiquity, it still makes a major impact on its
current constellation of residence, Taurus, looking like an extra star to the east of Aldebaran and the Hyades. The famed rings are now
seen as looking up from the south. Wide open, they reflect almost
as much light as the planet itself, enhancing the naked-eye view.
The rings seem to be the debris of a smashed satellite, or maybe
even the broken remains of a
comet, and consist of icy rocks only
a few centimeters across. They are among the thinnest things known
anywhere, the structures only a few hundred meters across, yet
nearly three hundred thousand kilometers wide. When they are
presented on edge, twice during the 29-earth-year Saturnian year,
they disappear from view.
Jupiter, rising two hours after Saturn, also has a ring system,
though one so faint that it is not visible from Earth, and
discovered close-up by the Voyager spacecraft. Jupiter's ring
seems to be debris from collisions on the inner satellites. From
Earth out, Mars, continuing to hang in the evening in the
southwest, is closest to us. Venus, the first planet in the
direction toward the INNER Solar System, continues to hang low in
the east just before sunrise.
The old summer stars, while still with us, are very much moving
into the west. Look in particular for Cygnus, the Swan. Tip it upside down, and you see the
Northern Cross, with the bright star Deneb at its top. At the bottom is
the famed double star Albireo.
Cygnus lies in one of the brighter parts of the northern Milky Way, which in the early evening
is best seen flowing through stars of Cassiopeia, nearly overhead for northerners and
recognizable by her famed "W" of stars. Both constellations
contain some of the most luminous stars in the Galaxy, Cassiopeia
boasting of otherwise un-named Rho
Cas, Cygnus of Deneb itself, a distant star that if placed a
mere 30 light years away would outshine Venus 40 times over.