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STEREO catches an eruptive prominence
Via Jenny Winder on Google+ I saw this way cool video of an eruptive prominence on the Sun: a towering arc of plasma held aloft by the Sun's magnetic fields. Sometimes these field lines are unstable, and the plasma can blast away from the Sun and out into space:
This video was taken by one of NASA's twin STEREO spacecraft; a pair of probes with one orbiting well ahead and the other behind the Earth. They stare at the Sun, literally giving us an angle on it we can't get from our planet. Specifically this was from the STEREO Ahead spacecraft, and combines an ultraviolet view of the Sun itself together with a visible light portion that shows the Sun's outer atmosphere, called the corona.
You can see the prominence form, rise up, and then erupt away into space over the course of one day, on October 6-7, 2012. Sometimes this material rains back down to the surface, and sometimes it escapes entirely. When it does the latter, it can flow outward, impact the Earth, and cause a geomagnetic storm. Usually those do us no harm, though if they get big they can disrupt satellites and potentially cause power outages. More likely they just create gorgeous aurorae which can be photographed from the ground.
It's actually rather amazing how many space-based eyes we have on the Sun and the amount of data they send back. The Sun is a feisty beast, and getting feistier as we approach the maximum part of its magnetic cycle. The more we observe it, the more we learn, and learning is always good.