|
 January 19, 2000 -- Each month
when the Moon is full, the coyotes in our neighborhood visit
my sled dogs' kennel. Three or four coyotes gather on one side
of the fence with about a dozen Siberian Huskies on the other.
Before long, the "Moon song" begins. It starts with
a few discordant yips and some tentative yowls. Then, just when
you think the chorus is over, there's a spine-chilling explosion
of howls in perfect canine harmony. No one sleeps through a full
Moon where we live.
The next full Moon is on Thursday and I fully expect the usual
serenade. But when my lead dog peers at the Moon this week, he
might do a double take. On Thursday night and Friday morning,
January 20 and 21, there will be a total lunar eclipse as the
Moon passes directly through the shadow of our planet. Unlike
a solar eclipse, which requires special equipment to observe
safely, a lunar eclipse can be viewed with the unaided eye, even
by Siberian Huskies.
Above: This time-lapse photograph
by Vic Winter shows a total lunar eclipse over North America
that occurred in April 1993. [more
information]
A lunar eclipse takes place when the
Moon passes through Earth's shadow. This can only happen when
the Moon is full. The eclipse will begin this Thursday night
when the moon is high in the sky over the Americas. The face
of the Moon will begin to dim at about 10 p.m. in New York and
7 p.m. in Los Angeles on January 20. As seen from Western Europe
and Africa, the eclipse won't begin until a few hours before
dawn on January 21. At totality the face of the Moon will likely
have a deep coppery color. [see the Eclipse
Time Table for details]
The Moon orbits the Earth every 29.5 days but it doesn't
pass through the Earth's shadow each time it goes around. That's
because the Moon's orbit is tilted with respect to the plane
of the Earth's orbit around the Sun. There are anywhere from
0 to 3 lunar eclipses (including partial and total) each year.
The last total lunar eclipse visible from the United States occurred
on Sept. 26, 1996. North Americans won't have another opportunity
to see a total lunar eclipse until May 16, 2003. However, on
July
16, 2000, Hawaii, Australia and Asia will see the longest
total lunar eclipse in 140 years (since 1859). It will last 1
hour and 47 minutes.
To fully understand lunar eclipses, you have to know the meaning
of umbra and penumbra. The Earth's shadow has a
conical shape with two parts. The umbral shadow (on the inside)
is very dark while the penumbral shadow (on the outside) is very
weak. An astronaut situated on the Moon inside the penumbral
shadow would see the disk of the Sun partially covered by the
Earth. From a position in the umbral shadow, the astronaut would
see a total eclipse of the Sun by the Earth.
Lunar eclipses are considered total when
the Moon passes completely into the umbral shadow. Unlike total
solar eclipses, which are over in just a few minutes, lunar eclipses
are slow. From start to finish, this week's lunar eclipse lasts
nearly three and a half hours. The eclipse begins as the Moon's
eastern edge slowly moves into the Earth's umbral shadow. During
this partial phase, it takes just over an hour for the Moon's
orbital motion to carry it entirely within the Earth's dark umbra.
Then, totality lasts for 77 minutes. After the total phase ends,
it is once again followed by a partial eclipse as the Moon gradually
leaves the umbral shadow.
You might think that the Moon would be completely dark at totality.
Not so. The Earth's atmosphere bends and refracts sunlight into
the umbra. Even at maximum eclipse the moon is weakly illuminated.
When this sunlight passes through Earth's atmosphere most of
the blue-colored light is filtered out. The remaining light is
a deep red or orange in color and is much dimmer than pure white
sunlight. The exact appearance depends on how much dust and clouds
are present in Earth's atmosphere. Total eclipses tend to be
very dark after major volcanic eruptions since these events dump
large amounts of volcanic ash into Earth's atmosphere. During
the total lunar eclipse of December 1992, dust from Mount Pinatubo
rendered the Moon nearly invisible. Since no major volcanic eruptions
have taken place recently, the Moon will probably take on a vivid
red or orange color during the long total phase.
During totality, the winter Milky Way and constellations will
be well placed for viewing. Gemini's Castor and Pollux lie a
dozen degrees northwest of the eclipsed Moon, while the Beehive
cluster or M44 is 7° to the east.
Total Lunar Eclipse of January 20, 2000
|
Event |
Time
GMT |
Time
EST |
Time
CST |
Time
MST |
Time
PST |
|
Partial Eclipse Begins |
03:01 AM* |
10:01 PM |
09:01 PM |
08:01 PM |
07:01 PM |
|
Total Eclipse Begins |
04:05 AM* |
11:05 PM |
10:05 PM |
09:05 PM |
08:05 PM |
|
Mid-Eclipse |
04:44 AM* |
11:44 PM |
10:44 PM |
09:44 PM |
08:44 PM |
|
Total Eclipse Ends |
05:22 AM* |
12:22 AM* |
11:22 PM |
10:22 PM |
09:22 PM |
|
Partial Eclipse Ends |
06:25 AM* |
01:25 AM* |
12:25 AM* |
11:25 PM |
10:25 PM |
* Event occurs on morning
of January 21, 2000
GST - Greenwich Mean Time; EST - Eastern
Standard Time; CST - Central Standard Time; MST - Mountain Standard
Time; PST - Pacific Standard Time |
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