A total solar eclipse was seen sweeping across Earth Friday morning,
providing a special glimpse of the sun for people in the upper Northern
The eclipse was visible in parts of Canada, northern Greenland, the
Arctic, central Russia, Mongolia, and China. According to NASA it will move across Earth in a narrow path that begins in Canada's northern territory of Nunavut and ends in northern China's Silk Road region at sunset.
A solar eclipse happens when the moon passes directly between Earth and the sun. When the moon's shadow falls on Earth, people within that shadow see the moon block a portion of the sun's light.
The moon's shadow has two parts, an umbra and a penumbra. The umbra is the main part of the shadow which appears to black out the sun. The umbra is the moon's faint "outer" shadow -- the outer ring of the main shadow.
During a total solar eclipse, the moon appears to cover all of the sun for observers located in the moon's umbral shadow. Those viewing the eclipse from the moon's penumbral shadow see the moon cover only a portion of the sun.
At the moment of "totality," when the moon's shadow totally obscures the sun, the sun's outer atmosphere -- the solar corona -- becomes visible. NASA says this seldom-seen sight -- visible for about two minutes at most -- is coveted by experienced eclipse watchers and an awe-inspiring vision for first-time viewers.
The solar corona extends farther than 620,000 miles from the sun's visible surface and reaches temperatures up to 2 million degrees.
Total solar eclipses happen once or twice a year somewhere in the world, but rarely hit in the same location.
"Just to say how special it is, in the whole universe we might be among the few beings that have the chance of seeing something like that," said
Michael Kahn, a mission analyst at the European Space Agency. "The fact that we have a moon and that the moon passes in front of our sun, and that the apparent size of our moon is approximately equal to the apparent size of the sun -- all these factors combine to create the solar eclipse phenomenon."
Those viewing any part of the eclipse should never look directly at it, experts warn. People can use a dense metalized plastic foil made specifically for viewing eclipses, available at opticians or astronomy shops, or they can mount telescopes or binoculars and project the image of the sun onto cardboard.