Speedster: One of the Fastest CMEs Ever

One of the top five fastest coronal mass ejections (CME) that scientists have ever observed, and the fastest observed by STEREO, blasted away from the Sun (July 22, 2012). It roared away at approximately 2930 km/s or 6.5 million mph, just over 1,800 miles per second. On average a CME moves at about 1-2 million mph. The STEREO (Ahead) spacecraft recorded the cloud's emergence on July 23rd starting around 0300 UT. The Solar Heliospheric and Observatory (SOHO), an ESA and NASA mission, also observed the CME. In fact, the positions of STEREO and SOHO are now just about optimal for detecting and clocking CMEs that are heading in any direction: the two STEREO spacecraft and Earth will form a rough equilateral triangle (~ 120 degree separations all around) next month.

The source of the CME was magnetic active region 1520 AR1520, which sparked many bright auroras earlier this month when it was on the Earth-side of the sun. When this CME erupted, the active region had rotated around to the Sun's far side so this blast was not geo-effective. The images combine data from two coronagraphs and an extreme UV imager on STEREO (Ahead). The heavy sprinkling of white streaks after the CME are protons striking the spacecraft's imagers.

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