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Q&A: Galaxies, Galaxy Clusters, AGN, and Quasars

Q:
Chandra Image of Bootes
Chandra Image of Bootes Field
Could you please give coordinates of the image center of the new Bootes Field image? Or could you possibly let us know which, if any, naked eye stars are in the field? It seems that anywhere one looks in the sky, one might be looking toward as many black holes (galaxies) as foreground stars (in our galaxy). Is this true?

A:
The approximate center of the Bootes field is given on our web-page as:

Coordinates (J2000): RA 14h 32m 00.00s | Dec +34 deg 06 min 00.0 s

At most directions in the sky the number of black holes and galaxies will outnumber the stars from our galaxy. This Bootes X-ray image is not a deep exposure at all and would have found many more black holes with more observing time. Good examples of this are the Chandra deep fields which are much deeper and manage to find hundreds of black holes despite covering much smaller regions of the sky.

http://chandra.harvard.edu/photo/2001/cdfs/
http://chandra.harvard.edu/photo/2001/cdfn/

These black hole catalogs are themselves incomplete, since "normal" galaxies likely contain dormant supermassive black holes (plus many smaller black holes) that don't shine brightly in X-rays.

If you look towards the center of a dense globular cluster you will have more stars from the galaxy than supermassive black holes in the background.

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