A high-mass Planetary Nebula in a Galactic Open Cluster
  Planetary Nebulae are the ionised ejected envelopes surrounding the remnant
cores of dying stars. Theory predicts that main-sequence stars with one to
about eight times the mass of our sun may eventually form planetary nebulae.
Until now no example has been confirmed at the higher mass range. Here we
report that planetary nebula BMP J1613-5406 is associated with Galactic star
cluster NGC 6067. Stars evolving off the main sequence of this cluster have a
mass around five solar masses. Confidence in the planetary nebula-cluster
association comes from their tightly consistent radial velocities in a
sightline with a steep velocity-distance gradient, common distances, reddening
and location of the planetary nebula within the cluster boundary. This is an
unprecedented example of a planetary nebular whose progenitor star mass is
getting close to the theoretical lower limit of core-collapse supernova
formation. It provides evidence supporting theoretical predictions that 5+
solar mass stars can form planetary nebulae. Further study should provide fresh
insights into stellar and Galactic chemical evolution.
