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Black Hole Ripples

June 30, 2016

It’s been only a few months since the first direct detection of gravitational waves — “ripples” in space and time created by the merger of two black holes. But astronomers have already come up with several scenarios to explain the history of the black holes themselves.

The basic facts are that one black hole was 36 times the mass of the Sun, the other 29 times the Sun’s mass. In the instant before they merged, they were orbiting each other at about half the speed of light. And the merger took place more than a billion light-years from Earth.

But how and where the black holes formed is less certain.

One idea says they were born 10 billion years earlier, from the collapse of mighty stars in the core of a giant cluster. Close encounters with other black holes kicked the tightly bound pair into intergalactic space.

Another idea says the black holes were “primordial” — they were born before the formation of any stars or galaxies, from the collapse of dense clumps of matter shortly after the Big Bang.

And yet another idea says the black holes were born from a single giant star. The star was spinning so fast that its core split into two clumps, each of which collapsed to form a black hole. Within a minute, material in the original star’s outer layers fell onto the black holes, increasing their heft. And in a few minutes more, the two black holes merged — creating waves in the universe that rippled past Earth last year.

Script by Damond Benningfield

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