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Music

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NASA's STEREO spacecraft

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resolved a 40-year mystery about how coronal mass ejections, or

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CME's, change shape during their long journey. With new data

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processing techniques, STEREO scientists have succeeded in continuously

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tracking space weather events from the Sun's ultra hot corona to

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the Earth, 93 million miles away. A CME

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is a huge, magnetized cloud of electrified gas, or plasma,

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that bursts out of the sun's atmosphere. It can be as big as one-and-a-half trillion tons of

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gas and travel at 3 million miles per hour.

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If a powerful CME hits the Earth's protective magnetosphere, it

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makes brilliant aurora, and can disrupt satellites, radio communications,

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and even our electrical power grids. Despite decades of observations

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with NASA's Heliophysics fleet of spacecraft, the details

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of the connection between activity on the sun and its effect on Earth has

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been poorly understood. This is because CMEs change while traveling

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from the sun to Earth and it's difficult to track their movement with only a

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head-on perspective. Now, with STEREO's two spacecraft

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sitting on either side of the sun, we can monitor the sky at large

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angles from Earth, and can see the full ocean of empty space between the sun

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and Earth. But CME's are some 10 billion times

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fainter than the full moon and were still too dark to see until

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scientists applied cutting-edge image processing techniques to separate

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the CME's from the starfield.

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By applying this new technology scientists

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were able to measure the absolute brightness of detailed features in the first

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large Earth-directed CME seen by STEREO, which occurred

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in late 2008. By the time the data were collected,

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STEREO-A was nearly 45 degrees ahead of Earth in its orbit,

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affording a very clear view of the CME's path from

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sun to Earth. For the first time ever,

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scientists can watch a CME from its formation on the sun to its

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impact with Earth's magnetosphere ending decades of speculation

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about how features in the sun's corona cause the massive, complex shape of a

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CME as it expands to ten million times

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its size. This new ability to see developing space weather during

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its entire transit from the Sun will enable scientists to better predict when

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and how a CME will impact Earth and understand how

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CME's change between the sun and our home.

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Music