Pulsar Jackpot in a Star Cluster

Editor’s note: AAS Nova is on vacation until 18 September. Normal posting will resume at that time; in the meantime, we’ll be taking this opportunity to look at a few interesting AAS journal articles that have recently been in the news or drawn attention.

Is Terzan 5, a star cluster that lies ~19,000 light-years away, a true globular cluster born in the Milky Way? Or are we seeing the remains of a dwarf galaxy that was captured by our galaxy? New observations by the Green Bank Telescope in West Virginia have tracked the radio signals of a treasure trove of millisecond pulsars — 36 of them — in the heart of Terzan 5. These signals can be used to trace the density distribution of the cluster, revealing where the matter resides. The observations, detailed in a recent article led by Brian Prager (University of Virginia, Charlottesville) and illustrated in the video below (credited to B. Saxton (NRAO/AUI/NSF); GBO/AUI/NSF; NASA/ESA Hubble), suggest that there is no supermassive black hole in the cluster center. This supports the idea that Terzan 5 is a true globular cluster.

Original article: Brian J. Prager et al 2017 ApJ 845 148. doi:10.3847/1538-4357/aa7ed7
Green Bank Observatory release: Pulsar Jackpot Reveals Globular Cluster’s Inner Structure