SIMBAD references

New observations of the planetary nebula PC 11, made in 1991, are presented and discussed. The object is a compact planetary nebula, small and dense, with a low mass of ionized gas. It is losing matter through one or more jets, formed mainly by O III. The central star is a binary, with a cool component of spectral type F0-F1 V. The hot component has an energy balance temperature of 105,000 K, a mass of 0.638 M_☉, and very low luminosity, estimated as 11 L_☉, with a radius of the order of 0.01 R_☉. The position of PC 11 in the H-R diagram is peculiar, since it seems incompatible with its being a very young planetary nebula, as suggested by its small size and high density.