Neutral Hydrogen Associated with the Planetary Nebula NGC 6302

Extract

Observations of HI in absorption made with the Very Large Array towards the thermal radio emission of the planetary nebula NGC 6302 show two velocity components at 6 and −40 km s⁻¹ (radial velocity with respect to the local standard of rest). The 6 km s⁻¹ component is almost certainly due to a line-of-sight cloud, but the −40 km s⁻¹ component is most probably associated with NGC 6302. We interpret this absorption component as coming from the neutral, outer part of an expanding (~ 10 km s⁻¹) ring whose inner part is ionized and produces the thermal continuum. The mass in atomic hydrogen of the outer (neutral) part of the ring is ~ 0.06 M_⊙. NGC 6302 is in an evolutionary stage intermediate to those of protoplanetary nebulae such as GL 2688 and evolved planetary nebula such as NCG 7293. This is the first detection of neutral hydrogen associated with a planetary nebula.