The expansion of the Cat’s Eye Nebula (medium zoom)

By looking at images of the Cat’s Eye Nebula taken by the NASA/ESA Hubble Space Telescope between 1994 and 2002 it is possible to discern the small difference in its size. Due to its unique position high above the disturbing clouds Hubble is the only telescope that can observe the expansion of planetary nebulae directly. The 1994 image was taken with Hubble’s Wide Field and Planetary Camera 2 (WFPC2) and the 2002 image with Hubble’s Advanced Camera for Surveys (ACS).

In order to show the expansion the animation is running back and forth in time a few times.

Credit: ESA/Hubble, the Hubble Heritage Team (STScI/AURA) and Romano Corradi (Isaac Newton Group of Telescopes, Spain)