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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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Galactic super-volcano in action

HST image of M87

This Hubble Space Telescope image shows the central core and accompanying outflowing "jet" of the giant elliptical galaxy M87. In the centre of the galaxy there lurks a supermassive black hole.

A galactic “super-volcano” in the massive galaxy known as M87 is erupting and blasting gas outwards, as witnessed by NASA’s Chandra X-ray Observatory and the US National Science Foundation’s (NSF) Very Large Array (VLA) of radio telescopes.

The cosmic volcano is being driven by a giant black hole in the galaxy’s centre and preventing hundreds of millions of new stars from forming.

At a distance of about 50 million light-years, M87 is relatively close to Earth and lies at the centre of the Virgo cluster, which contains thousands of galaxies.

M87’s location, coupled with long observations over Chandra’s lifetime, has made it an excellent subject for investigations of how a massive black hole impacts its environment.

Core of the galaxy M87

This is the core of the galaxy M87, seen at X-ray and radio wavelengths. A huge black hole, hiding in the middle, is ejecting energetic particles that push gas outwards. That gas would ordinarily form millions of new stars, so the black hole's activity is acting like a brake on star formation.

“Our results show in great detail that supermassive black holes have a surprisingly good control over the evolution of the galaxies in which they live,” said Norbert Werner of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the SLAC National Accelerator Laboratory, who led one of two papers describing the study.

“And it doesn’t stop there. The black hole’s reach extends ever farther into the entire cluster, similar to how one small volcano can affect practically an entire hemisphere on Earth.”

The space around M87 is filled with hot gas glowing in X-ray light, which has been detected by Chandra. As this gas cools, it should fall in toward the M87’s centre where it could continue to cool even faster and form new stars.

However, radio observations with the Very Large Array suggest that in M87 jets of very energetic particles produced by the black hole interrupt this process. These jets lift up the relatively cool gas near the centre of the galaxy and produce shock waves in the galaxy’s “atmosphere” because of their supersonic speed.

In M87, the plumes of cooler gas being lifted upwards contain as much mass as all of the gas contained within 12,000 light-years of the centre of the galaxy cluster.

This shows the black hole-powered volcano is very efficient at blasting the galaxy free of the gas that would otherwise cool down and form stars.

The eruption in M87 that lifted up the cooler gas must have occurred about 150 million years earlier, but a smaller eruption only about 11 million years earlier produced the shock wave.

Adapted from information issued by Chandra X-ray Centre.

Images courtesy Tod R. Lauer, Sandra M. Faber / NASA / X-ray (NASA / CXC / KIPAC / N. Werner, E. Million et al); radio (NRAO / AUI / NSF / F. Owen)

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