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

Title: 
X-Ray Stars of 47 Tucanae
Explanation: 
A deep optical image (left) of 47 Tucanae [ http://antwrp.gsfc.nasa.gov/apod/ap010422.html ] 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 [ http://chandra.harvard.edu/press/01_releases/press_051701.html ] its central regions (inset right) from the Chandra Observatory [ http://chandra.harvard.edu/press/fact7-1.html ] 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 [ http://imagine.gsfc.nasa.gov/docs/features/movies/ 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 [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ 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 [ http://www.sciencenet.org.uk/database/Physics/Stars/ p01158c.html ], neutron star [ http://www.astro.umd.edu/~miller/nstar.html ], or possibly a black hole [ http://antwrp.gsfc.nasa.gov/apod/ap010119.html ]. Chandra's x-ray vision [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ history1_xray.html ] detects the presence of an unexpectedly large number of these exotic star systems within 47 Tucanae [ http://chandra.harvard.edu/photo/constellations/ tucana.html ], but it also indicates the apparent absence [ http://oposite.stsci.edu/pubinfo/PR/2000/33/ index.html ] of a large central black hole. The finding suggests that compact binary star systems of 47 Tucanae [ http://www.seds.org/messier/xtra/ngc/n0104.html ] may be ejected from the cluster before coalescing to form a large black hole at its core [ http://antwrp.gsfc.nasa.gov/apod/ap980117.html ].
Credit and Copyright: 
X-Ray: J. Grindlay [ mailto: jgrindlay@cfa.harvard.edu ] (CfA [ http://cfa-www.harvard.edu/ ]) et al., CXO [ http://chandra.harvard.edu ], NASA [ http://www.nasa.gov/ ] Optical: W. Keel (U. Alabama Tuscaloosa) et al., 1.5-m Telescope [ http://www.astr.ua.edu/keel/telescopes/ctio.html ], CTIO [ http://www.ctio.noao.edu ]
keyword: 
binary star
facet_where: 
Alabama
facet_what: 
Crux
original url: 
http://antwrp.gsfc.nasa.gov/apod/ap010524.html
UID: 
SPD-APOD-ap010524