Skylights featured three times on Earth Science
Picture of the Day: 1
Photo of the Week.. The Sun, as seen with low
magnifying power on Thursday, October 30, 2003, displayed not one,
but two, gigantic sunspot groups on either side of the solar
equator. Note that the edge (the limb) of the Sun is dimmer
than the center (a phenomenon called limb darkening), a
consequence of the Sun being spherical and gaseous. The result is
that we look slightly deeper into the Sun at the center than at the
edge, and therefore to hotter and brighter gases.
Astronomy news for the week starting Friday, November 7, 2003.
This week we celebrate our two constant companions, the Moon and the Sun. The Moon begins the week not quite full, passing the
phase on Saturday, November 8, when it will plunge through the
shadow of the Earth to be eclipsed, the second total
eclipse of the year to be seen in North America. This one is
beautifully timed for the east, not quite so for the west. The
partial phase, wherein the Moon enters the full shadow of the
Earth, begins at 5:32 PM Central Time (add one hour for EST,
subtract an hour for MST, two hours for PST). For the eastern part
of the US and Canada, the eclipse will begin after sundown (and,
since the Moon is full, Moonrise). For the west, the Moon will
rise already partially eclipsed, actually producing quite the
fascinating sight. The Moon fully enters total shadow at 7:06 PM
(CST), leaves it at 7:31 PM, and then finishes the partial stage at
9:04. Totality does not last very long, as the Moon is a bit south
of the ecliptic, and really just clips full shadow. The shadow is
not fully dark, but is lit by sunlight scattered by and refracted
through the Earth's atmosphere, its brightness depending on
atmospheric opacity, mostly that caused by volcanic eruptions.
The result at central eclipse at 7:18 (CST) is that the south part
of the Moon will be notably brighter than the northern part, which
will be closer to the central part of the shadow.
The Sun (which with the Earth is the cause of the eclipse in the
first place) got additionally into the act through the great coronal mass ejection of
last week, the event caused by the collapse of magnetic fields
associated with the huge sunspot groups that paraded across the
apparent solar disk. (The "corona"
that surrounds the Sun and is seen during a solar eclipse is heated
to two million degrees and supported by solar magnetism.) Though
the Sun is now on the downside of its 11-year cycle, it is still
capable of producing powerful magnetic activity. The ejections
from the corona of the Sun hit the Earth and disturbed the magnetic
field, producing northern and southern lights, and disturbing
communications. More events are always possible (but impossible to
predict until we see the Sun actually eject the matter), so keep
your eyes on the nightly skies (though not on the Sun itself, which
is dangerous to look at).
Beyond the Moon and Sun, Venus,
slowly climbing the southwestern skies in evening twilight, passes
north of Antares in Scorpius the night of Sunday, November
9, the planet still difficult to see. The Moon will then be seen
to the northwest of Saturn
the night of Wednesday, the 12th, then to the northeast of it on
Thursday, the 13th. Mars, of course, still glowers to the south in the evening
hours, while bright
Jupiter dominates the early morning skies to the east, below
the brave figure of Leo.
This is Cassiopeia season, the
famed "W" appearing upside down as it crosses the meridian to the
north of overhead around 10 PM, the constellation that represents
the ancient Queen set within a remarkable part of the Milky Way,
which can be admired once the Moon moves out of the way.