The Life Cycle of a Black Hole

-- | March 14, 2013

Questions: Please may I ask some questions regarding black holes: — David

Have black holes always existed ever since the “Big Bang”?
What happens if two black holes were to collide, do they destroy one another or merge into an even larger black hole? Have scientist ever witnessed such an event?
What is the life span of a black hole and what happens to it in the end?

Answers:

There are theoretical predictions that suggest that black holes may have existed even *before* the Big Bang (during what some have called the “Big Crunch”, or the contractive event that preceded the Big Bang). These would be “primordial black holes”. The “normal” process for producing a Black Hole involves the collapse of a very massive (larger than 50 times the mass of our Sun) star as it exhausts its nuclear fuel. So, more standard theories would place the first Black Holes as forming only after the first massive stars formed, which happened when the Universe was about 200 million years old.
The collision and eventual merger of two Black Holes would indeed be a violent event. It would send out intense energy that would potentially be detected as a burst of gamma rays or gravitational waves. Such an event has never been identified, though.
It is not clear how Black Holes evolve, and if they have a lifespan. One theory predicts that a Black Hole will slowly radiate away mass via “virtual particles”. Note, though, that the existence of these virtual particles is in theory only.

Jeff Mangum

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