Image of the Day: The Deadly Beauty of a Super-Massive Black Hole


The super-active Circinus galaxy -only 4 degrees below the Galactic plane, and 13 million light-years away- belongs to a class of mostly spiral galaxies called Seyferts, which have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGN. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at its center.

Astronomers from Penn State University used Chandra to discover a variable object within the dozen or so X-ray emitting sources sprinkled throughout the Circinus galaxy. The intensity of X-rays from this source changes on a cycle of 7.5 hours – the first time this "periodic variability" has been detected at X-ray wavelengths in an object outside the "Local Group" of galaxies. And, along with its brightness, this evidence strongly suggests that the system contains a black hole some 50 times the mass of the Sun.

"Extremely luminous X-ray sources such as this one appear to be common among other galaxies," said Franz Bauer, a postdoctoral scholar at Penn State. "But until Chandra, we have never had an instrument that could clearly identify whether they were simply massive X-ray binary systems, or if they represented a new class of objects"

"The periodic variability in the Chandra data of Circinus provides us with a key signature that these objects are indeed X-ray binary systems," continued Bauer. "This is important because black holes with masses much larger than 10 times the mass of the Sun such as this one are difficult to explain under current theories of star formation and destruction. Definitively finding a periodic signal in one allows us to test some of our past assumptions."

Image Credit: NASA/Hubble


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