Last update: 31-Jul-2014 10:03 pm
Thursday, July 31, 2014
Trinidad & Tobago Guardian Online
You are here
Total lunar eclipse tonight
The first total lunar eclipse in more than two years will grace the skies tonight, and it will be visible from Trinidad and Tobago. Skygazers will have a front-row seat as the full moon is painted red, creating what many call a “blood moon,” as Earth’s shadow creeps across the lunar disk.
“Everyone should make an effort to see the lunar eclipse. It is a perfectly safe phenomenon for viewing and no special equipment is required. Simply look up and enjoy,” said Dr Shirin Haque, senior lecturer in the Physics Department of The University of the West Indies, St Augustine.
“Lunar eclipses are exciting because nature puts on a free show for everyone to enjoy, and it causes us to look back at the sky and re-examine our place in the solar system and beyond,” astronomer Raminder Singh Samra of the HR MacMillan Space Centre in Vancouver, Canada is quoted as saying in popular science magazine, National Geographic. Lunar eclipses occur only when there is a full moon and the sun, Earth, and moon are precisely aligned for our planet’s shadow to turn out the lunar lights.
During a lunar eclipse, the moon passes behind our planet so that Earth blocks the sun’s rays from striking the moon. Due to the moon’s tilted orbit around the Earth, one doesn’t occur every month. And total eclipses usually happen once every few years, though there are sometimes more than one in a year.
“Since the moon’s orbit around the Earth is slightly inclined, it doesn’t pass through the shadow every month, therefore every year we get an eclipse twice a year—very rarely we can get up to five,” said Samra. Unlike solar eclipses, lunar ones are safely visible to the unaided eye. A solar eclipse occurs when the moon comes between the Earth and the sun and blocks the disk of the sun.
Lunar eclipses have been considered an awe-inspiring sky event for millenia, and ancient astronomers could do rudimentary but fundamental science with them, says Samra. “Many cultures have mythologies associated with lunar eclipses so there has always been interest in the eclipses,” said Samra. Haque was quick to dispel the unscientific stories, however.
“There are old wives tales associated with eclipses and I get a lot of inquiries as to whether pregnant women should be out during an eclipse and about babies being born with cleft lips. There is no scientific reason that the eclipse should have any such effect on anyone. It is merely Earth’s shadow cast on the full moon which gives it an eerie red glow,” she said.
The best views will be from the entire North and South American continents. Europe, Africa, and central Asia, meanwhile, will miss the entire eclipse because it will be daytime in those regions at the time of the event.
Why is this eclipse noteworthy?
Beyond its occurrence over two heavily populated continents, next week's event kicks off a lunar eclipse tetrad (group of four). For two years, a lunar eclipse will occur over the Western Hemisphere every six months, on October 8, 2014 and April 4 and September 28, 2015.
Best time to look
The entire eclipse will last over three and a half hours, starting at about 2 am tomorrow morning, when the moon begins to plunge into the umbra, the darkest center of our planet’s shadow. The best part of eclipse will be during totality, starting at 3.07 am, lasting 78 minutes. After that, Earth's shadow begins to leave the surface of the moon. “The most spectacular part of the event for me is watching a slow progression of the moon changing color,” explains Samra.
“It will start off with the very familiar white but then progressively become fainter and then turn a deep red before emerging out of the Earth's shadow and returning to its familiar white color.” The height, or midpoint, of the total eclipse occurs at 3.46 am.
During an eclipse, sunlight shining through the ring of Earth’s dusty atmosphere is bent, or refracted, toward the red part of the spectrum and cast onto the moon’s surface. As a result, expect to see the lunar disk go from a dark gray color during the partial phase of the eclipse to a reddish-orange color during totality. The same effect is at work when the sun turns red at sunset.
The moon’s color during totality can vary considerably depending on the amount of dust in the Earth’s atmosphere at the time. Active volcanoes spewing tons of ash into the upper atmosphere, for instance, can trigger blood-red eclipses. No one can predict exactly what color we’ll see before each eclipse.