Today we offer a guest guest post from Dr. Richard L. White. Dr. White is an astronomer at the Space Telescope Science Institute and is the Principal Investigator for the Barbara A. Mikulski Archive for Space Telescope (MAST). He is a coauthor on several hundred papers covering topics ranging from cosmology, quasars, stars and galaxies to astronomical data processing and data mining. This article was previously posted at the Barbara A. Mikulski Archive for Space Telescopes news feed. For more information you can also check out our post about making the Hubble color image of Comet ISON.
Some bloggers have noted that the Comet C/2012 S1 (ISON) Hubble images seen here have some surprising features. Here we briefly explain the origin of the image structures.
Quick summary: The image is the result of combining three exposures that produce the three components, and the shapes are produced by the combined motion of the Hubble telescope and the comet. The images look exactly as expected.
The image from April 30, 2013 (released on July 16, 2013) using the F606W filter has attracted the most attention. That image (shown above) is the average of three separate Hubble exposures. The three exposures ...