What are those flying saucer-shaped objects in the LASCO images?
The “funny-looking spheroid” is a typical response of the SOHO LASCO coronagraph CCD detector to an object (planet or bright star) of small angular extent but so bright that it saturates the CCD camera so that “bleeding” occurs along pixel rows. There is a bright horizontal streak on either side of the image, because the charge leaks easier along the direction in which the CCD image is read out by the associated electronics. CCD stands for charge-coupled detector, and refers to a silicon chip, usually a centimeter or two across, divided into a grid of cells, each of which acts like a small photomultiplier in that an incoming photon knocks loose one or more electrons. The electrons are “read out” by row (fast direction) and column (slow direction), the current converted to a digital signal, and each cell or picture element (“pixel”) thus assigned a digital value proportional to the the number of incoming photons in that pixel (the brightness of the part of the image falling on that pixe
