Sunday, December 19, 2010

The Winter Solstice Lunar Eclipse

Every now and then you get a lunar eclipse on the winter solstice. That's just the way the geometry of the Earth/Moon/Sun system works out. Lunar eclipses are a pretty and easy to observe phenomena.

A lunar eclipse happens when the Moon is on the opposite side of the Earth from the Sun and passes through Earth's shadow. Lunar eclipses only happen when there is a full Moon. A lunar eclipse won't happen every time there is a full Moon since the Moon's orbit is inclined to the plane of the solar other words, the Moon will usually pass wither above or below Earth's shadow. Every now and then, everything lines up and you get the lunar eclipse.

This eclipse is well positioned for observers in North America, but you have to stay up a bit late. The penumbral eclipse starts at 1:29am eastern time. The penumbral phase is usually not impressive as the Moon is passing through the outer part of Earth's shadow and changes very little (although I have noticed the color of the Moon change from white to a pale yellow during this phase of the eclipse). The ubmral phase starts at 1:32am EST. That's when you notice the dark part of Earth's shadow starts covering the Moon. At this point, it's obvious something is going on. Totality starts at 2:40am EST and mid-eclipse is at 3:16am EST. Totality ends at 3:53am EST and the partial phases end at 5:01am EST.

During the total phases of the eclipse, you can usually still see the Moon as a deep red or orange color. Sometimes it is fairly bright while others it almost disappears. How bright it appears depends on lots of factors including how close to the center of the shadow the Moon passes and how much particulate matter is in Earth's atmosphere. With recent volcanic eruptions, it might be a bit darker of an eclipse than usual, but there is only one way to find out!

No telescope is required to watch the eclipse. Binoculars and small telescopes provide good view. Now just have to stock up on Red Bull to stay awake (or coffee for you coffee drinkers!)

Reprinted with permission from the Half-Astrophysicist Blog.

1 comment:

OrbsCorbs said...

Why do these things always happen at night? The National Wether Service currently predicts 1 to 3 inches of snow for Monday night/Tuesday morning in Racine. I probably wouldn't stay up that late anyway, but the pictures of eclipses are often beautiful.