The volcano-like eruptions at galactic hearts
For the first time, scientists have observed the large-scale impact that gas accelerated by a black hole has on the Universe. The structures formed by the gas, which resemble smoke streams produced by volcanic eruptions, were tracked on journeys lasting up to 100 million years.
Published in Nature Astronomy, the study demonstrates that the black hole in question - which sits some 200 million light years away - emitted matter beyond its own galaxy and into the intergalactic medium that surrounds it. In fact, the study suggests that the black hole impacted the Universe at distances up to 100 times larger than the galaxy it inhabits.
Understanding the mechanism by which black holes eject matter, and the rate at which they do so, is important for understanding how galaxies evolve. Marisa Brienza of the University of Bologna, and lead author of the study, explained this: “All of this energy that the black hole is releasing is really influencing the way the galaxy forms stars… Stars are formed by cold gas, which starts collapsing under the influence of gravity, but if this gas gets heated up - for example, by the energy released by a black hole - this gas will stop condensing and stop forming stars. So, it means that the galaxy overall will switch off; it will stop producing stars.”
The study was made possible by LOFAR, a network of radio telescopes spread across 52 European stations, which is able to measure the lowest frequency radiation currently detectable from Earth. As the gas released from the black hole gets accelerated across the Universe, it produces a type of radiation called ‘synchrotron radiation’, which LOFAR can pick up.
“This is really important to understand how it [star formation]… happens in a different way in different moments of the Universe's evolution; to understand how we got to the Universe as we see it now.”