PSR B1257+12 D

In performing the above comparisons, we have assumed that the current census (Konacki & Wolszczan 2003) of the pulsar planet system (which stands now at three objects) is complete. There have been reports in the past (Wolszczan et al. 2000b) of additional timing residuals in the B1257+12 data that might be indicative of the presence of additional small planets at larger radii. However, subsequent observations suggest these are due to effects related to the propagation of radio waves through the interstellar plasma, and not gravitational in origin (Alex Wolszczan, private communication).