Summary: / www.sciencexpress.org / 15 May 2008 / Page 1/ 10.1126/science.1158738
Observation of an eccentric millisecond binary pulsar
challenges the standard model of pulsar formation.
Pulsars are rapidly spinning neutron stars whose lighthouse-
like beams of radio waves sweep Earth, producing highly
regular pulses with periods ranging from about 1 ms to 8 s.
Of the ~1600 pulsars known in the disk of our galaxy, some
5% have pulse periods shorter than 10 ms (1). Most of these
millisecond pulsars have a companion star that is a white
dwarf, and all such millisecond binary pulsars known in the
galactic disk have perfectly circular orbits (1, 2). Yet, in this
week's Science Express, Champion et al. (3) report the
discovery of a millisecond pulsar in the galactic disk with a
highly eccentric orbit and a companion that is probably a
solar-like star. The mass of this pulsar is ~30% larger than
that of other binary neutron stars in the galactic disk (2). The
discoverers suggest that the high eccentricity of this binary is
due to interaction with a third star.
Neutron stars and black holes are the densest objects
known in the universe and have the strongest gravitational