We discovered 24 new millisecond pulsars in the globular cluster Terzan 5 using the S-band receiver of the Green Bank Telescope. This is now the globular cluster with the largest number of known pulsars, 27. These discoveries confirm fundamental predictions of globular cluster and binary system evolution. Thirteen of the new MSPs are in binary systems, of which two show eclipses and two have highly eccentric orbits. The relativistic periastron advance for the two eccentric systems indicates that at least one of these pulsars has a mass > 1.68 Msun at 95% confidence. Such large neutron star masses constrain the equation of state of matter above beyond the nuclear equilibrium density. The luminosity distribution indicates that there are about 100 active millisecond pulsars in the cluster detectable with an Arecibo-class radio telescope in the southern hemisphere. A survey effort is underway to use the same observing system to search for pulsars in other similarly rich globular clusters.

Reference: "Twenty-One Millisecond Pulsars in Terzan 5 Using the Green Bank Telescope",
Scott M. Ransom, Jason W. T. Hessels, Ingrid H. Stairs, Paulo C. C. Freire, Fernando Camilo, Victoria M. Kaspi, David L. Kaplan,
Science, 307, 892 (11 Feb. 2005)