Side by side, tw x-ray stars greeted astronomers inthis false-color Chandra Observator x-ray image of aregion near the core of globular starcluster M15.The greeting was a pleasant surprise, as all previous x-rayimages of the cluster showed only one such source wher Chandra'ssharper x-ray vision now reveals two.These x-ray sources are modeled a neutron starbinary systems.Each is a city-sized neutron star in close orbit witha normal stellar companion X-rays are generatedas matter from the normal sta falls ontothe compact neutron star This break through explainswhy observations of thepreviously recognized lone neutron star binary system in M15were difficult to reconcile with any single model.It also suggests that other globular star clusters whic roam the haloof our Milky Way galaxy an seem to containonly one such neutron star x-ray source may in fac contain more.An optical Hubble Space Telescope image of the dens M15 cluster is inset at the upper right.
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