October 4, 2012. Michael Eracleous

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On October 4, 2012, the University of Michigan invited Michael Eracleous to give a speech on black hole binary systems and mergers.



Eracleous, pictured below, is a memeber of the Penn state astronomy and astrophysics department.

Eracleous's speech was very detailed about black hole mergers. He focused on how black holes can merge under many different circumstances specifically in black hole binaries. Eracleous also discussed active galactic nuclei. Here is a little background information about AGN ( Active Galactic Nuclei).

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Black holes often are gravitationally attracted to each other. This is a proven fact because there are black holes that exceed billions of solar masses. When these black holes initially formed their masses were significantly smaller, so the only way they could have reached these high masses is through black hole mergers.

Astronomers also can estimate the time it takes black holes to merge. In about 4.5 billion years the Andromeda galaxy and the Milky Way galaxy will begin to merge. It will take about 12 billion years for the merger to complete. During the 12 billion years, the black holes at the center of the Milky Way and the center of Andromeda will “seek out” and find each other. Once the merger is complete there will be one big elliptical galaxy and one supermassive black hole at the center of the galaxy, but before the merger is complete these black holes will orbit each other in a binary “like” system. 

In a black hole binary system the two black holes circle each other and are gravitationally bound to each other. Eventually they get so close to each other that they fall into each other. The magnetic fields of the black holes are amplified and matter is evaluated. Then a funnel structure forms and the black holes become one single entity.  After black holes merge there is an accretion disk left behind and material from the accretion disk continuously falls into the black hole until there is no more material in the accretion disk.

Here is a video of this process:
 http://www.youtube.com/watch?v=ZIX2ngAwEn0