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National Aeronautics and Space Administration

Goddard Space Flight Center

Sun-Earth Day 2009: Our Sun Yours to Discover.

Sun-Earth Day 2009: Our Sun Yours to Discover



Active Region 9415 on 10 April 2001 at 06:00 UT in 171 (characteristic of emission from gas at 1 million Kelvin). The field of view is 232,000 by 174,000 km; the image was rotated over +120 degrees. These loops are the result of an X2.3 flare that started at 05:06 UT. The flare showed a classic double ribbon structure. As the ribbons spread apart with time the post-flare arcade of cooling, draining loops was formed, expanding with time.

This alignment of STEREO-B and the Moon is not just due to luck. It was arranged with a small tweak to STEREO-B's orbit last December. The transit is quite useful to STEREO scientists for measuring the focus and the amount of scattered light in the STEREO imagers and for determining the pointing of the STEREO coronagraphs.

The Sun as it appears in these the images and each frame of the movie is a composite of nearly simultaneous images in four different wavelengths of extreme ultraviolet light that were separated into color channels and then recombined with some level of transparency for each.


The August 4, 1972 solar flare was so powerful that, by some estimates, a spacesuited astronaut would have received a lethal does of radiation.