This a quote from : http://www.universetoday.com/2009/03...-cosmic-dance/
"If two black holes are present, they would orbit each other before merging and would have a characteristic dual signature in their emission lines. This signature has now been found."
Please , can somebody explain me why these BHs orbiting each other are due to merge.
Because , you know , with ordinary celestial bodies like Earth and the Moon or the Sun and the planets , the merging never happen. So why do BHs merge ?
Has the cause something to do with the accretion disks around the BHs ? Or some magic relativity trick ?
Thanks in advance.