Black holes were early starters

Galaxy M87

The galaxy M87, about 100 times bigger than our Milky Way, is home to a giant black hole. The galaxy and its black hole could have been among the earliest to form after the Big Bang.

  • Big galaxies formed quickly after the Big Bang
  • So did black holes, and the two are probably connected
  • Giant galaxy M87 is probably one of those first galaxies

Astronomers think they have nutted out the origin of our Universe’s first super-massive black holes, which formed some 13 billion years ago.

In the journal Nature, Ohio State University astronomer Stelios Kazantzidis and colleagues describe computer simulations in which they modelled the growth of galaxies and black holes during the first few billion years after the Big Bang.

For more than 20 years, the prevailing wisdom had been that galaxies evolved slowly as gravity drew small bits of matter together first, and those small bits gradually came together to form larger structures and so on.

But recently, other astronomers determined that big galaxies formed much earlier in the Universe’s history than previously thought—within the first 1 billion years. (The Universe is thought to be 13.7 billion years old.)

Computer simulation of two galaxies merging

Computer simulation of two galaxies merging (from top left). The result is a giant galaxy with a huge black hole in its core (bottom right).

The new computer simulations show that the first super-massive black holes were likely born as a result of those big galaxies colliding and merging.

Matter is thought to be a mixture of “normal matter”—eg. stars, galaxies and black holes—and “dark matter”, some as-yet-unknown and invisible stuff that far outweighs the amount of normal matter.

Kazantzidis and his team found that while dark matter grouped together in the early Universe in a slow, step-by-step fashion, normal matter formed into “clumps” in a much faster manner. And so “…our result shows that big structures—both galaxies and massive black holes—[built] up quickly…” he said.

They also found that smaller structures like our own modest Milky Way galaxy—and the comparatively small black hole at its centre—formed more slowly.

The merged galaxies in which the first super-massive black holes formed are still around today, Kazantzidis says.

“One of them is likely our neighbour in the Virgo Cluster, the elliptical galaxy M87,” he said. “The galaxies we saw in our simulation would be the biggest galaxies known today, about 100 times the size of the Milky Way. M87 fits that description.”

Adapted from information issued by Ohio State University / CFHT.

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