Event Horizon targets the Centaurus A radiogalaxy

AstronewsOther Galaxies

The Event Horizon Telescope (EHT) zooms in on the heart of the Centaurus A radio galaxy, a 55 million solar mass black hole 11 million light-years from Earth. After the first historic photo of a black hole, it gives us another stunning image with a level of detail never seen before.

Details never seen before

Scientists from the Event Horizon Telescope collaboration used observations from various radio telescopes to photograph the heart of Centaurus A radio galaxy. International group achieved a level of detail never seen before, at a wavelength of 1.3mm. The same technique used to create the first photo of a black hole at the center of the M87 galaxy,

The team was able to identify the probable location of the supermassive black hole at the center of the same radio galaxy, revealing the birth of a giant jet. To their surprise, scientists discovered that only the outer edges of the jet seem to emit radiation, which overthrows all current theoretical models. The EHT data dates back to the 2017 campaign and images have been obtained with a resolution 16 times clearer than previous high-resolution images.

“EHT’s images show the jet of Centaurus A with a spectacular level of detail” explains Kazi Rygl, researcher and member of the EHT scientific team in the article (ref.) on Nature. “The revelation of the illuminated edges of both the jet and the counter-jet, the latter much less luminous, allows us to study their collimation profile. In a few words, we determine the angle, the approximate position of the jet apex, and that of the black hole”

How do black hole jets like Centaurus A form?

Supermassive black holes located at the center of galaxies like Centaurus A feed on gas and dust. The process releases massive amounts of energy, making the galaxy active. Some particles escape just before being captured by the black hole’s gravity and are projected into space at speeds close to that of light. This is how jets are formed and there are several theoretical models that try to describe their behavior. But it is still unknown how jets are launched from regions close to the black hole and how they can propagate to vast distances without dissipating.

This new image shows that the Centaurus A jet is brighter at the edges than in the center. A phenomenon already known for other jets, but never seen in such a pronounced way until now. “Even though the black hole at the center of Centaurus A is too small to see its ‘shadow,’ its proximity to Earth has allowed us to study it. For the first time, we have studied an extragalactic radio jet on scales equal to about six times the distance between the Sun and Neptune adds Ciriaco Goddi, researcher at the University of Nijmegen in the Netherlands. “EHT provides a wealth of data on a wide range of black holes. And we’re just getting started”.

Researchers predict that they will be able to directly observe the black hole at the center of the radio galaxy using an interferometric observatory in orbit. Ideas for this already exist. For example, Theza (TeraHertz Exploration and Zooming-in for Astronomy) is proposed for the European Space Agency‘s (ESA) Voyage 2050 program.

Stefano Gallotta
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