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Published Online August 25 2011
Science DOI: 10.1126/science.1208890


Transformation of a Star into a Planet in a Millisecond Pulsar Binary


M. Bailes1,2,3,*, S. D. Bates4, V. Bhalerao5, N. D. R. Bhat1,3, M. Burgay6, S. Burke-Spolaor7, N. D’Amico6,9, S. Johnston7, M. J. Keith7, M. Kramer8,4, S. R. Kulkarni5, L. Levin1,7, A. G. Lyne4, S. Milia9,6, A. Possenti6, L. Spitler1, B. Stappers4, W. van Straten1,3

Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719−1438, a 5.7 ms pulsar, was detected in a recent survey with the Parkes 64 m radio telescope. We show that it is in a binary system with an orbital period of 2.2 h. Its companion's mass is near that of Jupiter, but its minimum density of 23 g cm−3 suggests that it may be an ultra-low-mass carbon white dwarf. This system may thus have once been an Ultra Compact Low-Mass X-ray Binary, where the companion narrowly avoided complete destruction.

PSR J1719−1438 demonstrates that special circumstances
can conspire during binary pulsar evolution that allows
neutron star stellar companions to be transformed into exotic
planets unlike those likely to be found anywhere else in the
Universe. The chemical composition, pressure and
dimensions of the companion make it certain to be
crystallized (i.e., diamond).

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