Cosmic! Millions watch as total eclipse plunges US into darkness

Millions of people looked on as the Moon blocked out the Sun in the first total solar eclipse in a century to cross the US.

Spectators wore protective glasses as the Moon created near-darkness and caused a significant drop in temperatures as the eclipse reached "totality" for several minutes.

Crowds cheered and clapped in Depoe Bay, Oregon, where the "totality" - the moment the Sun is completely blocked - began.

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The phenomenon arced across the country, taking three hours to reach people in South Carolina on the east coast.

And eagle-eyed stargazers would have spotted the International Space Station (ISS) travelling across the surface of the Sun before totality was achieved.

The last time a total eclipse took place from one US coast to the other was in 1918, and the last total eclipse anywhere in the US was in 1979.

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The event was expected to draw one of the largest audiences in history, with 7.4 million people expected to journey into the eclipse's 2,500-mile path.

For people outside the zone of totality, a partial eclipse was visible.

In Washington DC, hundreds waited in lines outside the National Air and Space Museum to get free viewing glasses and watch the spectacle.

President Donald Trump, along with First Lady Melania and his son Barron, watched the partial eclipse from the Truman balcony at the White House.

The President squinted at the sky as it began - an eclipse no-no - before stopping to put on protective glasses.

One of his aides reportedly warned him "don't look" when he took off his glasses for a moment.

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Many people trekked to national forests and parks in Oregon, Idaho and Wyoming to get the best view.

Cities including Kansas City, Missouri, and Nashville were along the path of the eclipse.

During a total eclipse, light dims to almost twilight and stars and planets become visible.

The last glimmer of light as the Moon covers the Sun then gives way to a momentary sparkle known as the "diamond ring" effect - where the aura of the Sun's outer atmosphere, or corona, is visible.

At this stage the temperature dropped, birds quietened down and prepared to roost, and crickets chirped.

NASA reported 4.4 million people were watching its TV coverage midway through the eclipse - the biggest live-streamed event in the agency's history.

Scientists from NASA and other organisations are hoping to learn more about the Sun's composition and activity after watching from telescopes on the ground and in orbit on the ISS, airplanes and high-altitude balloons.

Astronomer Dr David Whitehouse told Sky News about the "mysterious" corona around the Sun, which burns at millions of degrees.

"It's full of structure, it's full of worlds, it's full of filaments," he said.

"You saw little red flashes around, which are prominences moving above the Sun... things being thown out above the Sun, falling back on the Sun and some of them escaping completely."

He said scientists analyse the light to see what is there and how it moves, adding: "It's a wonderful spectacle but some fantastically interesting science".

"Some of the scientists may actually have been too busy to properly take a look at what they were seeing."

Total eclipses usually take place every one to three years for a small sliver of the planet, but they often take place in no man's land like at the poles.

The next total solar eclipse will be visible from South America in 2019 and again in 2020.

Antarctica will get a total solar eclipse in 2021 and Iceland will see one in 2026.