Introduction
The Event Horizon Telescope has expanded its collection of images of black holes. In 2019, the telescope unveiled the first image of a black hole, revealing the massive beast located 55 million light-years away from Earth at the center of the galaxy M87. The tilted orange ring showcased the shadow of the black hole against the luminous accretion disk of falling materials. Since then, observations from the Event Horizon Telescope have provided even more detailed images of the black hole in M87. Now, Event Horizon data has revealed new details about the massive black hole in the heart of a nearby galaxy called Centaurus A.
New Details About the Black Hole in Centaurus A
Instead of zooming in enough to see the shadow of the black hole, the new image provides the clearest view yet of the powerful plasma jets emanating from the black hole. This insight offers a deep look into how such massive black holes blow these plasma jets into space, researchers report in their online paper published on July 19, 2021, in the journal Nature Astronomy.
Radio astronomer Craig Walker says, “It’s a relatively impressive achievement” to capture the new high-resolution image. “These jets are among the strongest things in the universe,” says Walker from the National Radio Astronomy Observatory in Socorro, New Mexico, who was not involved in the work. Because he believes that such fast plasma jets influence the growth and evolution of galaxies, astronomers are eager to understand how these jets form.
The New Imaging of the Black Hole in Centaurus A
The researchers directed the global array of satellites that form the Event Horizon Telescope toward Centaurus A for six hours in April 2017, during the same observation period that provided the first image of the black hole. Centaurus A is about 12 million light-years from Earth and is one of the brightest galaxies in the sky, known for the massive jets expelled by its central black hole.
Michael Janssen, a radio astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany, says, “It extends across almost the entire scale of the galaxy.” “If we could see the radio light [with our eyes] and looked at the night sky, we would see those jets in Centaurus A as a structure that is 16 times larger than the full moon.”
Using the Event Horizon Telescope, Janssen and his colleagues focused on the base of those jets that emanate from either side of the accretion disk of the black hole. The new image is 16 times clearer than previous observations of the jets, revealing details less than one light-day apart – about four times the distance between the Sun and Pluto. One of the prominent features revealed by the image is that it appears only the outer edges of the jets are glowing.
Janssen states, “That remains a mystery.” One possibility is that the jets are rotating, which could cause materials in certain regions of the jets to emit light toward Earth while not doing so in other regions. Alternatively, the jets could be hollow.
Recent observations of some other galaxies have suggested that jets from massive black holes are brighter around the edges, according to Denise Gabuzda, an astronomer at University College Cork in Ireland, who did not participate in the work. Gabuzda says, “But it is challenging to determine whether this is a common feature, or it’s something peculiar to the few that have been observed.”
The next step will be to compare the Event Horizon image of Centaurus A with computer simulations based on Einstein’s general theory of relativity, to test how well relativity holds up in this extreme environment. Analyzing the polarization or direction of the light waves emitted from Centaurus A’s jets could also reveal the structure of its magnetic fields – much like how polarization revealed the magnetism around the black hole in M87.
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Source: https://www.sciencenews.org/article/black-hole-picture-centaurus-a-galaxy-massive-jets-event-horizon
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