SIMBAD references

Optical imaging and spectroscopy reveal that the ionised region No.252 in the list of Marsalkowa (1974Ap&SS..27....3M), whose photograph is presented in the ``Atlas of Galactic Nebulae'' by Neckel & Vehrenberg (1990), is actually a planetary nebula. According to Acker et al. (1992ESOPN...1....1A), the object should therefore be named as PN G321.6+02.2. The nebula has the following properties: it is located at 2.0±0.5kpc from the Sun, has a bipolar morphology, a giant size (∼4pc!), low densities, a hot (unobserved) central star (T>130000K), and extreme He and N overabundances (He/H=0.147±0.029, log(N/O)=0.47^+0.20_–0.38). The nebula is likely to be in a very evolved evolutionary stage.