A total lunar eclipse, the longest in eleven years, will take place on June 15th, the first of two that will happen this year.
Lunar eclipses occur when the moon passes behind the earth, causing the earth to block the sun’s rays from reaching the moon. Total lunar eclipses can only happen when the sun, earth, and moon are aligned exactly or almost exactly, with earth in the middle. Total lunar eclipses account for 35% of all lunar eclipses. Lunar eclipses can only occur when there is a full moon. Seemingly, there would be a lunar eclipse every month during the full moon, but the orbit of the moon prevents eclipses from happening monthly. The moon does not orbit the earth on the same ecliptic plane between the sun and the earth; instead, it orbits approximately 5 degrees off of the ecliptic plane. The place where the moon does occasionally cross the ecliptic plane is called a node. In order for an eclipse to happen, the moon must be near a node.
The earth creates two cone-shaped shadows: the umbra (the center shadow) and the penumbra (the outer shadow). Both of the cone-shaped shadows are cast from behind the side of the planet being hit by the sun. During a total lunar eclipse (as opposed to a penumbral eclipse or a partial eclipse), the moon enters the umbral shadow, which is encased by the penumbral shadow. Every total lunar eclipse starts with a penumbral eclipse, followed by a partial eclipse, before entering into a total eclipse. The moon then enters another partial eclipse before ending with a final penumbral eclipse. The penumbral phase of an eclipse is the most difficult to view, even with the aid of a telescope.
Lunar eclipses last for several hours at a time and always happen on a night with a full moon. The upcoming eclipse is expected to last for just over five and a half hours. The period known as totality, which occurs when Earth’s shadow blocks the moon completely, will last for one hour and forty minutes. This is seven minutes longer than the lunar eclipse that occured on July 17, 2000, when the moon was completely eclipsed for 107 minutes.
During a total lunar eclipse, the moon changes from a white glow to an orange or reddish haze. When the moon is completely in the umbral shadow of the earth, it is still exposed to indirect sunlight. Before the sunlight reaches the moon, however, it must pass through Earth’s atmosphere, which filters out most of the blue colored light. The only light that remains, then, is orange or red. The atmosphere of the earth bends and refracts this light so that it reaches the moon, casting it in an eerie reddish glow. The color of the moon during a total lunar eclipse is influenced by the presence of dust or clouds in the earth’s atmosphere; the more debris that is present, the darker the moon appears.
Lunar eclipses can generally be viewed from anywhere on earth at night, unlike solar eclipses, which are only visible from certain parts of the planet. Also unlike solar eclipses, lunar eclipses can be viewed with a naked eye. Because the upcoming lunar eclipse is a central eclipse, it will be visible over Europe and South America after sunset, and over Africa, Asia, and Australia before sunrise. Unfortunately, the lunar eclipse will not be visible in North America. The next total lunar eclipse that will be visible in North America will take place on April 15th, 2014.
The most recent total lunar eclipse occured on December 21, 2010. After June 15th, the next total lunar eclipse will take place on December 10, 2011. Several solar eclipses have also happened this year, both partial: one on January 4th and one on June 1st.
The upcoming eclipse will begin at 1724 GMT and last until 2300 GMT.
Photo Credit: apod.nasa.gov/apod/image/0007/nzeclipse_munford_big.jpg