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December 4: An Active Sun During a Total Eclipse

  December 4: An Active Sun During a Total Eclipse  
  An Active Sun During a Total Eclipse  


This image was originally used for NASA's Astronomy Picture of the Day click on the above image for the article



The above picture is a combination of three separate images taken in very different ways. The image of the Sun, the "solar disk", was taken with SWAP on PROBA2 from a sun-synchronous low Earth orbit. Off-disc, the SWAP image (yellow) has been overlaid with an image from the total eclipse that occurred November 3, 2013, observed by the Williams College Eclipse Expedition on ground in Gabon. The outer image (grayscale) is a coronagraph image from the LASCO instrument aboard SOHO spacecraft. Coronagraphs create an artificial eclipse, in which a solid disc in front of  the instrument (rather than the moon) blocks the Sun. By blocking the bright solar disk we're able to track the relatively dim outflowing solar atmosphere, the corona, into interplanetary space.

Because the sun is so bright, the coronagraph occulter—that is, the disc that blocks the sunlight—must be much larger than the visible sun in order to block scattered light sufficiently to see the faint corona. Total solar eclipses, however, allow us to view the corona in white-light nearly to the corona's sources on the sun's surface. Unfortunately, the rarity of total eclipses makes observations of the corona in such detail hard to obtain. Thus solar scientists travel to the remotest corners of the world to observe the corona for just a few minutes during eclipses.

Click here to learn more about coronagrapghs. Click here to learn more about eclipses and eclipse science.

Image credit: D. Seaton (ROB), A. Davis & J. M. Pasachoff (Williams College Eclipse Expedition), NRL, ESA, NASA, NatGeo.