Discovery of Multiple Shells Around the Planetary Nebula IC 418
  We have analysed optical, near-, and mid-IR images of the bright planetary
nebula (PN) IC 418. These images probe unambiguously for the first time a
number of low surface brightness structures and shells around the bright main
nebula, including radial filaments or rays, a system of three concentric rings,
and two detached haloes with sizes ~ 150" and 220"\times250", respectively. The
main nebula is slightly off-centered with respect to the elliptical outer halo.
The time-lapse between the two haloes is 10,000-50,000 yr, whereas the
time-lapse between the three concentric rings is ~ 630 yr. We emphasize the
advantages of near- and mid-IR imaging for the detection of faint structures
and shells around optically bright nebulae.
