A plenitude of pulsars
Globular clusters -- thick clumps of very old stars lying just beyond the fringes of the Milky Way -- seem a surprisingly fertile breeding ground for rapidly spinning neutron stars, or pulsars. Although these clusters, satellites of our galaxy, lie so far away that astronomers can detect only the brightest pulsars, a systematic search for pulsars within globular clusters has already pushed the tally to 20. The results suggest that a typical globular cluster may harbor at least 100 pulsars, most of which woudl be too faint to detect. Such an abundance is difficult to reconcile with conventional models of the evolution and dynamics of globular clusters.
In the latest discovery, reported in the July 5 NATURE, a research team from the California Institute of Technology in Pasadena identified two additional pulsars in a globular cluster designated Messir 15 by sifting through radio-wave signals captured at the Arecibo radiotelescope in Puerto Rico. Their find brings to three the number of known pulsars in that star grouping. …