Two months before the first total solar eclipse to cross the continental United States in a century, NASA on Wednesday is expected to detail its plans to study and promote a celestial show that will darken skies from Oregon to South Carolina.

During the Aug. 21 eclipse, the moon will pass between the sun and Earth, blocking the face of the sun and leaving only its outer atmosphere, or corona, visible in the sky.

It is the first coast-to-coast total eclipse since 1918.

Weather permitting, astronomy enthusiasts can watch as the moon's 70-mile (113-km) wide shadow crosses the country, starting at 10:15 a.m. PDT (1715 GMT) around Lincoln Beach, Oregon, and ending at 2:49 p.m. EDT (1849 GMT) in McClellanville, South Carolina.

The U.S. National Aeronautics and Space Administration will discuss several solar physics and Earth science experiments to be conducted during the eclipse in a news conference on Wednesday afternoon. The agency also plans live broadcasts during the eclipse from dozens of locations along the path.

Total solar eclipses occur somewhere on Earth every year or so, but most cast their shadow over oceans or remote land. The last time a part of the contiguous U.S. saw a total eclipse was in 1979.