A total solar eclipse was sweeping across Earth Friday, providing a rare sight for people in the upper Northern Hemisphere.

The eclipse will be visible in parts of Canada, northern Greenland, the Arctic, central Russia, Mongolia, and China. It will move across the planet in a narrow path that begins in Canada's northern territory of Nunavut and ends in northern China's Silk Road region at sunset, according to NASA.

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.

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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 can still be a special experience for viewers.

"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 Khan, 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 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 on to cardboard.

Source:CNN

PASADENA, California (AP) -- At least one of many large, lake-like features on Saturn's moon Titan contains liquid hydrocarbons, making it the only body in the solar system besides Earth known to have liquid on its surface, NASA said Wednesday.

Scientists positively identified the presence of ethane, according to a statement from NASA's Jet Propulsion Laboratory in Pasadena, which manages the international Cassini spacecraft mission exploring Saturn, its rings and moons.
Liquid ethane is a component of crude oil.
Cassini has made more than 40 close flybys of Titan, a giant planet-sized satellite of the ringed world.

Scientists had theorized that Titan might have oceans of methane, ethane and other hydrocarbons, but Cassini found hundreds of dark, lake-like features instead, and it wasn't known at first whether they were liquid or dark, solid material, JPL's statement said.
"This is the first observation that really pins down that Titan has a surface lake filled with liquid," Bob Brown, team leader of Cassini's visual and mapping instrument, said in the statement.

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The instrument was used during a December flyby to observe a feature dubbed Ontario Lacus, in the south polar region, that is about 7,800 square miles, slightly larger than North America's Lake Ontario.

Cassini reached Saturn in mid-2004 and at the end of that year launched a probe named Huygens that parachuted to the surface of Titan the following January.

The mission is a project of NASA, the European Space Agency and the Italian Space Agency.


Source: CNN