A new look at Centaurus A

The Event Horizon Collaboration’s Earth-wide telescope network targeted another black hole: the center of the galaxy Centaurus A, which is about 13 million light-years away, and is particularly “high” in the radio wave range. Instead, the images display the plane with a precision unattainable before. It can be seen, among other things, that its features match those of radiation and particle streams in the much larger M87* black hole, but also that the edges of the jet emit most of the radio radiation. This calls into question a number of theoretical models for how aircraft operate.

When active black holes devour matter, they often create huge jets of particles and high-speed radiation. These objects race through space at nearly the speed of light and transfer energy and matter over vast distances—often far beyond the black hole’s original galaxy. But it is not clear how and where these streams of radiation and particles originate and where their enormous energies come from. The differences between different types of black holes relative to their planes are only partially known because high-resolution images and data are often missing. That’s where the Event Horizon Telescope (EHT) comes into play: because the resolution of its radio telescopes, paired together by interferometry, matches an Earth-sized antenna, it can even image distant jets with greater accuracy than all the telescopes in front of it.

Centaurus planes on the horizon

One of the things the EHT focused on as part of its observations is the black hole at the center of the Centaurus A galaxy, about 13 million light-years away. Powerful cosmic radio sources since 1949. Michael Jansen of the Max Planck Institute for Radio Astronomy in Bonn and colleagues explain that “Centaurus A is the closest high-sound radio source to Earth.” This is why it has already been investigated at almost all electromagnetic wavelengths. From this data we know that the black hole at the center of the galaxy should be about 55 million solar masses. The astronomers say: “In terms of mass and rate of accumulation, it is located between the supermassive black hole of the galaxy M 87 with a mass of six and a half billion solar masses, and that is in the center of our galaxy, which contains about four million solar masses.” It was also known from previous observations that Centaurus A *like M87* is producing a jet.

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Jansen and his team observed this plane and its likely location using the Event Horizon Telescope. To do this, they used data from eight radio telescopes, located primarily in the Southern Hemisphere and thus having a clear view of Centaurus A. Among them were the Atacama Large Millimeter/ Submillimeter Array (ALMA), the Atacama Pathfinder Experiment (APEX) in Chile, and the James Telescope Clerk Maxwell in Hawaii, and the Antarctic Antarctic Telescope. In a coordinated action on April 10, 2017, telescopes pointed their antennas at Centaurus A for six hours and picked up radio radiation in the 1.3 mm wavelength range. Processing your data now leads to the most accurate radio recordings of a Centaurus A. jet to date.

Hypothetical approximation: resolutions of previous recordings for Centaurus A and EHT recordings in comparison. (Image: Radboud University; CSIRO/ATNF/I.Feain et al., R.Morganti et al., N.Junkes et al.; ESO/WFI; MPIfR/ESO/APEX/A. Weiss et al.; NASA/ CXC/CfA/R. Kraft et al. TANAMI/C. Mueller et al. EHT/M. Janssen et al.)

Noticeably lighter edges

The new recordings show Centaurus A with a nominal precision of 25 microarcseconds – 16 times higher than previous recordings – and a frequency 10 times higher. “This allows us, for the first time, to examine an extragalactic radio jet at scales smaller than the distance traveled by light in a day. We see up close how a very massive jet is being generated, starting from a supermassive black hole,” says Jansen. Heading to the northeast and approaching us at an angle. The opposing jet directed to the southwest can be seen with much less force. The Centaurus A jet in its primary structure and main features are consistent with those of the most massive black hole M87*. Astronomers report: “Through our observations, we prove The fundamental relationships of activity and jets of black holes are valid for objects of both sizes.”

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One feature that both planes show is particularly interesting: The plane flying from the center of Centaurus A is also brighter at the edges than at the center. This phenomenon has already been observed in other aircraft, but has not been shown in this detail. “Now we can rule out all theoretical jet models that cannot reproduce this edge brightness. It is an amazing observing feature that will help us better understand the jets generated by black holes,” says co-author Matthias Kadler of the University of Würzburg. On the location of the black hole of Centaurus A. An apple on the moon.At the same time, their data indicate that the shadow of this supermassive black hole can become visible at radio frequencies of a few terahertz and by means of a telescope network that also includes an orbiting radio telescope.

Source: Michael Jansen (Max Planck Institute for Radio Astronomy, Bonn) et al., Natural Astronomy, doi: 10.1038/s41550-021-01417-w

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