Detail View: NASA Astronomy Picture of the Day Collection: X-Ray Stars of 47 Tucanae

X-Ray Stars of 47 Tucanae
A deep optical image (left) of 47 Tucanae [ ] shows an ancient globular star cluster so dense and crowded that individual stars can not be distinguished in its closely packed core. An x-ray image of [ ] its central regions (inset right) from the Chandra Observatory [ ] reveals a wealth of x-ray stars hidden there. Color-coded by energy, low energies are red, medium are green, and high energy cosmic x-ray sources [ cinema.html ] are blue, while whitish sources are bright across the x-ray energy bands. The x-ray stars here are double stars or "compact" binary star systems [ binary_stars.html ]. They are so called because one of the pair of stellar companions is a normal star and the other a compact object -- a white dwarf [ p01158c.html ], neutron star [ ], or possibly a black hole [ ]. Chandra's x-ray vision [ history1_xray.html ] detects the presence of an unexpectedly large number of these exotic star systems within 47 Tucanae [ tucana.html ], but it also indicates the apparent absence [ index.html ] of a large central black hole. The finding suggests that compact binary star systems of 47 Tucanae [ ] may be ejected from the cluster before coalescing to form a large black hole at its core [ ].
Credit and Copyright: 
X-Ray: J. Grindlay [ mailto: ] (CfA [ ]) et al., CXO [ ], NASA [ ] Optical: W. Keel (U. Alabama Tuscaloosa) et al., 1.5-m Telescope [ ], CTIO [ ]
binary star
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