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]
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.
|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
Sky & Telescope Press Release -On Thursday night/Friday morning, January 20/21, Americans and Western Europeans will have a front-row seat for the first total lunar eclipse in more than two years.
Total Lunar Eclipse: January 20-21, 2000 - a press release from the Goddard Space Flight Center
More information about the eclipse -from Fred Espenak at the Goddard Space Flight Center
Tips for photographing a lunar eclipse -an excellent overview from MrEclipse.com
5000 year catalog of lunar eclipses -During the 50 century period, 2000 B.C. to 3000 A.D., Earth experiences 12186 lunar eclipses.