Radio maps of the proto-planetary nebula GL 618 have been obtained with angular resolutions as high as 0.07 arcsec. A bright radio core of 0.4 arcsec x 0.1 arcsec is found to be surrounded by a halo of several arc seconds in size. The core shows an elongated structure having the same symmetry axis as the optical reflection nebulosities. It is suggested that the ionized region of GL 618 is ionization bounded in the equatorial directions, and the bipolar morphology is the result of an anisotropic density distribution in the circumstellar envelope of its red-giant progenitor. The small angular size and high emission measure (greater than 10 to the 10th /cm to the -6th power/pc) of the core suggest that GL 618 is a planetary nebula of extremely young age (approximately 100 yr).
No takes yet. Share an insight, caveat, or question.
Kwok et al. (1984) studied this question.