total lunar eclipse 2011

Lunar Eclipse

Category: Astronomy • Solar System
Posted on: June 14, 2011 2:40 PM, by Ethan Siegel

"It is one of life's bitterest truths that bedtime so often arrives just when things are really getting interesting." -Lemony Snicket

Those of you who live basically anywhere other than North America are in for a treat this Wednesday. All over Earth, of course, the Moon is nearing its "full" phase, where the half of the Moon illuminated by the Sun is completely visible from Earth.

And it will reach complete fullness on Wednesday night.

Now, most times, when this happens, the full Moon is completely visible from everywhere on Earth. But every so often -- about twice a year on average -- the Earth's shadow falls on the full Moon, causing a lunar eclipse.

And the one happening this Wednesday is visible almost all places on the Earth. Reaching its point of greatest eclipse at about 8:12 PM, Universal Time (which is about 4:12 PM, Eastern Daylight Time in the US), you might think you're likely to see a sight much like this.

After all, the Moon doesn't disappear during a total lunar eclipse, but rather turns red, as a result of sunlight refracting through the Earth's atmosphere, and more red light landing on the Moon than blue light.

(Image credit: Stanley David Getzelman.)

But the coming lunar eclipse is special for two reasons. Normally, the Moon is closer to one end of the Earth's shadow than another, and so the side closest to the edge appears whiter, while the portion closest to the center appears redder.

But for this coming eclipse, the Moon passes almost dead center through the Earth's shadow.

(Image credit: F. Espanek and NASA/GSFC.)

So what you're actually likely to see, if you watch it over the whole span of the eclipse, is a sight much more like this one:

It's very rare to see the Moon be an almost uniform, red color; this only happens when the Moon passes through the dead center of the Earth's umbral shadow!

But passing through the center of the Earth's shadow means a second remarkable thing as well: this lunar eclipse will be long.

(Video credit: youtube user MentalLapse.)

With a full 50 minutes of total eclipse on either end, we get a total eclipse lasting an hour and 40 minutes, the longest of the new millenium thus far. In addition to that, there's an hour of partial eclipse to be had on either side of that, and another hour (for you true eclipse fanatics) of penumbral eclipse on either side of that.

All told, it means everyone across the world -- basically except for North America -- is going to get to see something.

(Image credit: F. Espanek and NASA/GSFC.)

So if you've got clear skies at all, know your time zone and don't miss it!

For those of you -- like me -- in North America, we're not totally left out! Remember how I said these happen, on average, every six months? Come back out on December 10th, just before dawn, and enjoy the second total lunar eclipse of the year!