Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. September 2004 morning sky: The
overexposed crescent Moon sits in central Gemini with Castor and Pollux to the left of it. Below the
Moon are Saturn and Venus, while Orion rises to the right with Sirius below.
Astronomy news for the short week starting Saturday, October
23, 2004.
The Moon starts its week in the waxing gibbous
phase as it heads toward full, the phase reached the night of
Wednesday, October 27, when there will be a magnificent lunar eclipse that is beautifully timed for
continental North America.
On that night, the Moon will pass just to the north of the central
part of the Earth's
shadow. The "penumbral phase" (when the Moon falls into
partial shadow of the Earth) is only barely visible and is here
ignored. The Moon begins to enter total shadow (called the
"partial eclipse phase" because only part of the Moon is obscured)
at 8:14 PM CDT. (Add an hour for EDT, subtract an hour for MDT, 2
hours for PDT; subtract another hour if you are on standard time).
The eclipse then becomes total at 9:23 PM
CDT. Mid-eclipse, when the Moon is as dark as possible, falls at
10:04 PM CDT. The events then reverse, with the Moon beginning to
leave the total shadow at 10:45 PM CDT, the show over at 11:54 PM
CDT. While Alaskans will see the eclipse, Hawaiians will see only
the last parts of it.
Since the Earth's atmosphere scatters sunlight into the realm of
total shadow, the Moon does not become completely dark during totality.
The brightness of the eclipsed Moon depends on the state of the
terrestrial atmosphere, particularly on the degree of volcanic
activity prior to the eclipse, as dust and aerosols dim the amount
of light getting through. The colors on the Moon can be quite
lovely, especially if the eclipse is viewed with binoculars or a
telescope.
As anticlimax,
Neptune, deep in Capricornus,
ends
retrograde motion on Sunday, the 24th.
The morning sky near dawn does much better
with the planets, where brilliant Venus
clearly rules. However, look below Venus to find bright
Jupiter, which is now clearing the horizon in modest twilight.
In the other direction, to the west, find Saturn, which is
now rising just after 11 PM Daylight Time. Though still in Gemini, Saturn is very close to the
border with Cancer, and is nicely
pointed to by Gemini's Pollux and
Castor.
As the Moon dims into totality, watch the stars come back out.
Since the Sun is now well past the autumnal equinox, the fully eclipsed Moon will be the
same degree to the east of the Vernal
Equinox, and south of the classic figure of Aries. To the southwest lies
Neptune's Capricornus, one of the
dimmer Zodiacal constellations,
while the Summer Triangle of
Deneb, Vega, and Altair moves off to the northwest.
