10 December 2011
The total lunar eclipse of 4 May 2004
Photo by Aymen Ibrahem
On 10 December 2011, a total lunar eclipse will be visible worldwide, in most of Africa, Europe, Asia, Australia and North America. Unlike eclipses of the Sun, lunar eclipses are safe to view with the unaided, unprotected eye.
In Egypt, the Moon will rise eclipsed, about the time of sunset, at 4:54 p.m., Cairo local time. The partial stage of the eclipse ends at 6:18 p.m., local time, when the Moon leaves the dark central part of Earth’s shadow. The eclipse ends at 7:30 p.m., local time, when the Moon exits Earth’s shadow entirely. During the eclipse, the Moon will shine low in the sky, above the eastern horizon.
This map shows the visibility of the 10 December total lunar eclipse. The eclipse will occur during moonrise in Egypt. The eclipse will be visible in all continents, except for South America and Antarctica.
Credit: Fred Espenak (NASA GSFC)
Lunar eclipses are among the most beautiful natural phenomena. They occur when the Moon passes through Earth’s immense shadow. At this time, Earth, the Moon and the Sun are exactly or nearly aligned. Earth’s shadow extends for about 1.4 million km in space, and is approximately 10,000 km wide, at the distance of the Moon’s orbit. (The average distance of the Moon is about 384,000 km.) From our view on Earth, Earth’s shadow is circular in shape. It consists of a dark inner component, known as the umbra, and an outer pale component, called the penumbra.
This illustration shows the path of the Moon through Earth’s shadow, during the 10 December 2011 total lunar eclipse. The eclipse starts at 11:33:32 UT, when the Moon touches the penumbra, represented as a grey circle, at point P1. This stage is the penumbral eclipse. It is less noticeable than the following partial and total phases of the eclipse. The partial eclipse begins at 12:45:42 UT, when the Moon touches the umbra, represented as a red circle, at point U1. The total eclipse is at 14:06:16 UT, when the lunar disc touches the umbra at point U2. Totality ends at 14:57:24 UT, when the Moon’s limb is tangent to the umbra at point U3. At U4, the partial eclipse ends, at 16:17:58 UT. When the Moon is tangent to Earth’s shadow at P4, at 17:30:00 UT, the Moon is completely out of Earth’s shadow, and the eclipse ends.
Credit: Fred Espenak (NASA GSFC)
There are three types of lunar eclipses: total, partial and penumbral. A total lunar eclipse occurs when the Moon passes completely inside the umbra. Interestingly, the Moon does not disappear, during totality, but glows faintly, due to refraction of sunlight by Earth’s atmosphere. If Earth were airless, the Moon will be dark during totality.
A partial lunar eclipse occurs when only a portion of the Moon enters the umbra. A penumbral eclipse takes place when the Moon travels within the penumbra. It is less noticeable than the partial and total eclipses.
Aymen Mohamed Ibrahem
Senior Astronomy Specialist