Chandra/HST image of M15
Credit: Chandra: NASA/GSFC/N.White, L.Angelini; HST: NASA/HST -- P. Guhathakurta (UCO/Lick Observatory, UC Santa Cruz), B. Yanny (Fermi National Accelerator Lab), D. Schneider (Pennsylvania State Univ.), J. Bahcall (Inst. for Advanced Study

Resolving Globular Neutron Stars

Globular clusters are balls of hundreds of thousands or millions of ancient stars; they represent regions of the highest stellar density in our galaxy. One particularly interesting question is how many of the stars in globulars have evolved into ultradense neutron stars. But because of the high concentration of stars, answering such questions has been a real challenge, somewhat like finding a needle in an astronomical-sized haystack. But astronomers are rapidly making progress thanks to high spatial resolution cameras on the Chandra X-ray observatory, and thanks to the excellent imaging provided by the Hubble Space Telescope in the optical. The images above show 2 views of the globular cluster M15. As can be seen in the image on the right, Hubble sees literally thousands of stars in the cluster; trying to identify the neutron stars in the cluster from Hubble images would take years or decades. But the X-ray cameras on Chandra show that the cluster is only composed of 2 X-ray bright stars, readily identifying two neutron stars in the cluster. The exquisite images produced by Chandra allow astronomers to pinpoint the location of the two neutron stars, enabling them to pick out these two neutron stars from among the thousands that Hubble sees. The Chandra observation also doubles the number of neutron stars in M15- earlier X-ray observations could not resolve the 2 neutron stars from each other, causing astronomers to mistakenly believe that there was only one neutron star in M15.

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Page Author: Dr. Michael F. Corcoran
Last modified December 10, 2001