TOWARD PLANETS AROUND NEUTRON-STARS

The two Earth-like mass objects orbiting a 6.2-ms pulsar, PSR1257+25, have survived more than one year of close scrutiny aimed at verifying their existence and remain the most serious candidates to become the f irst planets detected beyond the Solar System. The analysis of systema tic timing measurements of the pulsar made over a 2.5-year period cont inues to require the presence of two planets with the minimum masses o f 3.4 M+ and 2.8 M+ and the corresponding distances from PSR1257+12 of 0.36 AU and 0.47 AU to correctly predict the pulse arrival times. The presently available 3 mus rms accuracy of this procedure leaves littl e room for significant contributions to the pulsar's timing from any m echanisms other than the Keplerian motion. A detection of the effect o f planetary perturbations on pulse arrival times which is commonly acc epted as the most convincing way to furnish a ''100% proof'' of the re ality of pulsar planets is already possible at a approximately 2sigma level. Intensive searches for millisecond pulsars now under way at var ious observatories are expected to address a very intriguing question of the frequency of occurrence of neutron star planetary systems.