SIMBAD references

We report the measurement of the angular expansion rate of the compact planetary nebula Vy 2-2. Four epochs of radio continuum maps over a total time baseline of 15 years (1982-1997) and covering a wide band of frequencies are used to deduce the expansion rate. The variations in the observed flux densities at 1.5, 4.9, 8.4, 15, and 23 GHz and the variations in the observed radius deduced from the 15 GHz visibility data are used to compare with various simple models. The two methods provide a clear and consistent detection of the expansion. The resulting value of the angular expansion rate is 1.13±0.12 mas.yr^–1. A self-consistent solution from the flux density models indicates that the ionized shell is a density-bounded region. The kinematic age of the nebula, derived from the angular expansion, of 213 ± 26 yr confirms that Vy 2-2 is an extremely young planetary nebula.