Four thermal IR images of Hale-Bopp showing the increase in brightness and complexity of the inner coma from June through September 1996. The tick marks represent the offset from the nucleus in arc seconds.
North is up and East is to the left.
A strong 8 - 12 micron silicate emission feature is visible on each date, and a narrower bump near 11.2 microns is due to crystalline olivine grains. The curves drawn through the endpoints indicate the approximate underlying continuum emission. Structure near 9.5 microns is due to improper cancellation of telluric ozone absorbtion while dividing by the standard star spectrum.