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Astronomers just found a radio galaxy that turned out to be a blazar: Science Alert -Se

Astronomers have observed a rare phenomenon of changing galaxy size.

Decades ago, an object called PBC J2333.9-2343 located about 630 million light-years away was classified as a massive radio galaxy. It also projected large, radio-emitting structures perpendicular to our line of sight, formed by massive jets that once erupted from the galactic center.

More recent observations, however, reveal that the galactic core has restarted, and is now aiming its jet directly at us.

It’s nothing to panic about; In fact, it’s fairly common. So common, in fact, that we have a name for it; A blazer With its new classification, the blazar PBC J2333.9-2343 gives us a deeper understanding of how galaxies can evolve, even On human duration.

Galaxies come in different shapes and sizes, but they also have different activity levels based on the activity of the supermassive black hole at their core. For example, the Milky Way is a relatively peaceful galaxy; Our supermassive black holes are fairly inactive, accreting only small amounts of material.

A supermassive black hole that is positively churning up dust and gas from its surroundings looks very different. This material forms a torus and disk that surrounds the black hole; Due to the extreme gravity and frictional forces this disc glows with light across the entire electromagnetic spectrum.

From the inner edge of the disk, material falls onto the black hole, like water swirling down a drain. But all those elements do not end beyond the event horizon. Some of it flows out of the black hole along the magnetic field lines and is accelerated. When it reaches the poles, this material is ejected into space at great speed, creating jets of plasma that blast into space at a significant percentage of the speed of light in a vacuum.

An image of PBC J2333.9-2343 obtained using PAN-STAR. (University of Hawaii Astronomy Institute)

When the black hole finishes its meal and cools down again, what’s left of those jets can travel out into space, breaking out into lobes that continue to emit radio waves. These are known as giant radio galaxies and can be massive. PBC J2333.9-2343 contains such radio lobes, evidence of past black hole activity, at a total distance of 3.9 million light years.

But the galaxy showed some strange behavior at different wavelengths, leading a team of astronomers led by Lorena Hern├índez-Garcia of the Millennium Institute of Astrophysics in Chile to hypothesize that PBC J2333.9-2343 may now be a blazar. they are published a paper outlining their argument in 2017And now they’ve got observational evidence to match.

“We started studying this galaxy because it shows strange properties,” Hernandez-Garcia explained. “Our assumption was that the jet changed its direction relative to its supermassive black hole, and we had to do a lot of observations to confirm that idea.”

The research team conducted a very thorough investigation, collecting observations at radio, infrared, optical, ultraviolet, X-ray and gamma-ray wavelengths. Then, they compared their observational data with a large database of blazar and non-blazar galaxies.

The results show that the properties of J2333.9-2343 are more consistent with blazar galaxies, suggesting that the galaxy has been dramatically redirected by 90 degrees so that its black hole aims one of its jets at us.

“We can see that the nucleus is no longer feeding the lobes, which means that they are very old.” Hernandez-Garcia said. “These are remnants of past activity, while structures near the nucleus represent young and active jets.”

How a black hole can change position so dramatically is still unknown. There is a distinct lack of activity between the lobe and the galaxy, suggesting that the black hole was knocked sideways during a major event, such as a collision and merger with another galaxy.

Instead, it could mean that we are detecting, for the first time, what the researchers call a “very exceptional case of jet rearrangement,” transforming J2333.9-2343 and leading to its reclassification from a massive radio galaxy to a blazar. .

Published in research Monthly Bulletin of the Royal Astronomical Society.

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