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Beyond The Veil: The Search for Hidden Black Holes, a.k.a. Type 2 Quasars

March 20, 2000 ::

Superman (Superman: Copyright DC Comics)
Episode 1
Could giant black holes be hiding in the centers of galaxies that lead double lives, appearing as mild-mannered "Clark Kent-like" normal galaxies in visible light, but revealing a powerful "Superman-like" inner core in X-rays? Many astronomers think so, but no one has ever been able to prove it. Now, using Chandra, a group of 10 English and one French astronomer have published observations of an object that appears to be an optical "Clark Kent" galaxy with a camouflaged "Superman," a.k.a. a Type 2 quasar,

NGC 5548 Composite NGC 5548 X-ray/Optical comparison
Type 2 quasars are predicted by a popular model for quasars, called the unified model. This model is an extension of an earlier model used to explain galaxies that show unusual energetic activity in their central regions. These regions are called Active Galactic Nuclei, or AGNs, and have been categorized into two types:

  • Type 1 AGNs show evidence of energetic activity in the form of hot, rapidly moving gas clouds, and bright radio emission, and low energy X-ray emission.
  • Type 2 AGNs show evidence of less energetic activity in the form of scattered light and gas moving at moderate speeds, some radio activity in the form of jets, and no low energy X-rays.
The AGN unified model, developed by astronomers Robert Antonucci, of the University of California, Santa Barbara, and Joseph Miller of the University of California, Santa Cruz, proposed that Type 1 and Type 2 AGNs could have a common explanation - a donut-shaped veil of gas and dust around a central black hole.

To be continued...

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