Astronomers from the Event Horizon Telescope (EHT) collaboration imaged a jet at the core of the nearby Centaurus A radio galaxy and identified the location of the galaxy’s central supermassive black hole relative to its resolved jet core.
Centaur A is located some 13 million light years away in the constellation Centaur.
First discovered in 1826 by Scottish astronomer James Dunlop, it is a massive elliptical radiogalaxy – a galaxy that emits strong radio waves – and is the largest, and by far the closest, galaxy. radio in the sky.
Also known as NGC 5128, LEDA 46957, and ESO 270-9, Centaurus A is also the closest active galactic nucleus to us.
Astronomers theorize that what was originally an elliptical galaxy collided with a relatively smaller spiral-shaped galaxy, giving it the particular shape we see now.
At the heart of Centaurus A is a supermassive black hole with a mass of 55 million solar masses.
It bridges the gap in mass and accretion rate between the supermassive black holes of Messier 87 and our own Milky Way galaxy.
“Supermassive black holes residing at the center of galaxies like Centaurus A feed on gas and dust attracted by their enormous gravitational pull,” said Dr Michael Janssen, astronomer at the Max-Planck-Institut für Radioastronomie and Radboud University , and his colleagues in the EHT Collaboration.
“This process releases massive amounts of energy and the galaxy is said to become active.”
“Most of the material near the edge of the black hole falls off. However, some of the surrounding particles escape moments before capture and are thrown far into space: jets – one of the most mysterious and energetic features of galaxies – are born. “
Compared to previous observations, the EHT imaged the Centaurus A jet at ten times the frequency and sixteen times sharper resolution.
“This allows us for the first time to see and study an extragalactic radio jet at scales less than the distance light travels in a day,” said Dr Janssen.
“We are seeing firsthand and personally how a monstrously gigantic jet launched by a supermassive black hole is being born.”
The new EHT image shows that the Centaurus A jet is brighter at the edges compared to the center. This phenomenon is known from other jets, but has never been seen in such a pronounced way before.
“Now we are able to rule out theoretical models of jets unable to reproduce this edge brightening,” said Professor Matthias Kadler, astronomer at the University of Würzburg.
“This is a striking feature that will help us better understand the jets produced by black holes.”
Astronomers have discovered that the source structure of Centaurus A resembles the Messier 87 jet.
In addition, they identified the location of Centaurus A’s supermassive black hole in relation to its jet core resolved at a wavelength of 1.3 mm and concluded that the shadow of the event horizon of the source should be visible at terahertz frequencies.
“These data come from the same observation campaign that delivered the famous image of the Messier 87 black hole,” said Professor Heino Falcke, astronomer at Radboud University.
“The new results show that the EHT provides a wealth of data on the rich variety of black holes, and there is more to come.”
The team’s article was published in the journal Nature astronomy.
Mr. Janssen et al. Observations of the Event Horizon telescope of the launch and collimation of the jet in Centaurus A. Nat Astron, published online July 19, 2021; doi: 10.1038 / s41550-021-01417-w