Wednesday, December 7, 2011

Don't miss the upcoming Total Lunar Eclipse on December 10, 2011

As the second and last of two total lunar eclipses in 2011, the total lunar eclipse occurring on 10 December is posed to enthrall eclipse-enthusiasts from central and eastern Asia, Australia, New Zealand, Alaska and northern Canada. The first total lunar eclipse was observed on 15 June this year. The eclipse’s total phase would last for meager fifty one minutes. Its faint penumbral shadow would begin to cover moon at 17:16 hours local time. The dark umbral phase would touch the moon at 18:30 hours. The moon would enter into totality at 19:51 hours and would arrive at the maximum phase of the greatest eclipse at 20:17 hours. The umbral eclipse magnitude would reach 1.11 at this stage. The totality end at 20:43 hours and the umbral shade would recede from the moon fully at 22:03 hours. The entire eclipse would be finally over at 23:16 hours.

How can you do Lunar eclipse observation?

They are safe to watch with naked eyes. Unlike solar eclipse, which can only be gazed briefly from any specific place, a lunar eclipse can be perceived for several hours. It could provide enthralling targets for avid photographers as well.

How does eclipse occur?
A lunar eclipse takes place when the Sun, earth and moon are all perfectly aligned with the earth sitting in the middle of Sun and moon. When the moon passes behind earth, the Sun's rays are blocked from striking the moon. This can only happen when the moon is full and the moon is near or at the descending or ascending nodes (two points of intersection between the planes of moon’s orbit with that of earth’s path around Sun). This time the moon is at the descending node that lies in eastern region of zodiacal constellation Taurus (bull) four days after apogee (moon’s furthest point from earth).

Types of lunar eclipse
Astronomers recognize three basic types of lunar eclipses. In penumbral lunar eclipse the moon passes through earth's penumbral shadow. These events are of only academic interest because they are subtle and hard to perceive. In partial lunar eclipse a portion of the moon passes through earth's umbral shadow and can be admired easily with unaided eye. At total lunar eclipse the entire moon steeps into perplexing earth's umbral shadow of vibrant red color.

Why does not the lunar eclipse happen each month?
Even though the moon orbits earth every 29.5 days and lunar eclipses occur at full moon, lunar eclipses do not happen every month during full moon. It is because the moon's orbit around earth is inclined sparsely five degrees to earth's trajectory around Sun. There are two points (ascending or descending nodes) where the lunar path intersects earth’s track. Since earth's shadows lie exactly in the same plane, during full moon, our natural satellite usually passes above or below earth's shadows and misses them completely. No eclipse takes place. When two to four times each year, moon finds itself at or near the nodes to pass through some portion of the earth's penumbral or umbral shadows, one of the three types of eclipses can be witnessed. Everyone on the night side of earth can see lunar eclipse. Thirty five percent of all eclipses are of the penumbral nature. Another thirty percent are partial eclipses. Around thirty five percent are fascinating total eclipses.

Future Total Lunar Eclipse
Though 2012 and 2013 are devoid of total lunar eclipses, they could be relished in 2014, 2015, 2018, 2019 and 2021.

Source: Press release sent by NASO on December 7, 2011.

No comments:

Post a Comment