Core of globular clusters viewed by IUE: Evidence for black holes found


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The International Ultraviolet Explorer (IUE) satellite reveals conditions inside globular clusters that may be used to test for the presence of black holes.

Ultraviolet instrumentation on the IUE allowed a team of astronomers led by Andrea Dupree and Herbert Gursky, both of the Harvard-Smithsonian Center for Astrophysics, to observe the cores of globular clusters. The team is studying six globular clusters, three of which are X ray sources. Globular clusters are, in effect, miniature galaxies. Each contains tens of thousands of tightly packed stars. Scientists believe that globular clusters which are distributed above and below the pinwheel disk of the galaxy in the galactic halo are as old as the galaxy. They may even have contained the first stars to appear in the galaxy. Many astronomers have suggested the possibility that a massive black hole—perhaps as large as a thousand solar systems—is at the core of some globular clusters in our own galaxy and that these black holes are responsible for the intense X ray emission and X ray bursts found to emanate from them.