Discovery of multiple shells around the planetary nebula IC 418

Abstract

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 arcsec and ?, respectively. The main nebula is slightly off-centred 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.