Number 54 (Story #4), November 4, 1991 by Phillip F. Schewe and Ben Stein HOW COULD A PLANET BE ORBITING A PULSAR? Scientists at the University of California at Santa Cruz (Stan Woosley, 408-459-2976) suggest that the 10-Earth-mass planet orbiting pulsar 1829-10 is not a pre-existing planet which happened to have survived the supernova that gave birth to 1829-10. Instead, they believe, it formed from supernova debris falling back (at first) to a disk; from this, later, several 100-km planetesimals formed and later still these coagulated into a planet. A rival theory, presented by Julian H. Krolick (301-338-7926) at Johns Hopkins, holds that the pulsar companion began as a star, much of whose bulk was ablated through its interaction with the pulsar. (Nature, 31 October 1991.)