Did The Sun Do a 360 While NASA Was Away?
By Space Coast Daily // October 18, 2013
NASA's Solar Dynamics Observatory video
NASA.gov — Here’s what the sun looked like while we were away. These images were captured from Oct. 1, 2013 through Oct. 17 by NASA’s Solar Dynamics Observatory (SDO).
On Oct. 2, the sun appears to spin completely around its axis, but of course it was really SDO that did the 360. SDO rolls around its axis twice a year to help calibrate one of three instruments aboard SDO — the Helioseismic and Magnetic Imager.
The roll helps scientists remove optical distortions from the images and so precisely determine the boundaries of the sun’s horizon, or “limb”. Accumulated over time, such data shows whether the sun’s sphere changes in concert with the 11-year solar cycle, during which the sun moves through periods of greater and lesser activity as evidenced by the changing frequency of giant solar eruptions.