Planetary Nebulae Expansion Distances.
Session 51 -- Planetary Nebulae
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [51.10] Planetary Nebulae Expansion Distances.

Hajian A.R., Terzian, Y (NAIC, COrnell Univ.), Bignell, C. (NRAO)

As part of a continuing program to estimate the distance to planetary nebulae (PNe), we have applied an expansion parallax algorithm to six sources: NGC 2392, NGC 3242, NGC 6210, NGC 6572, NGC 7027, and BD+30--3639. The algorithm requires two Epochs of data obtained at the VLA at $\lambda$6 cm. With only 6 years between Epochs, we have accurately measured the angular expansion rate of the target PNe with errors that are typically $\sim$10\%. By combining the detected expansion rate with the expansion velocity, we have directly computed the distance to these nebulae with accuracies that represent significant improvements over the current estimates in the literature. We analyze the implications of the new distances on the physical conditions in all such measured nebulae to date.