A team of astronomers from the National Center for Radio Astrophysics in India discovered a Giant Radio Galaxy (GRG) nine billion light years away through the Giant Metrewave Radio Telescope (GMRT). The galaxy is said to be in its dying phase, thereby providing experts with information regarding the structure of galaxies that are about to fade away.

Radio galaxies discharge strong radio waves that obscure the optical signals of similar galaxies. Those that are enormous in size are very rare and the newly discovered one, named J021659-044920, emits radio signals equivalent to an extent of four million light years.

Despite its mighty ability to produce such massive radio waves, the J021659-044920 is only a few hundred thousand light years in optical size. This then raises questions of how such an optically-sized galaxy generates multi-million light years worth of radio waves.

Experts said that a huge black hole at the center of the galaxy pushes big scale jets of hot plasma to move in opposite directions, resulting in large radio lobes that are emitted into space.

The black hole may eventually stop generating radio jets under special conditions. When this happens, the illuminating radio lobes fade away within millions of years because of inadequate resumption.

The recent discovery of the J021659-044920 is something extraordinary because the astronomers were able to catch it during its dying stage. The radio jet looks as if it has been turned off and the radio lobes have began dwindling.

Fading radio lobes are said to be caused by energy loss through two possible ways. The first mechanism is via the so-called inverse Compton scattering, characterized by the transfer of energy from the radio lobes to the photons of cosmic microwave backdrop. Such process leads to the creation of a dim X-ray emission. Another possible way by which energy may be lost is by releasing radio signals, which are presented as the gigantic radio lobes.

"Our work presents a case study of a rare example of a GRG caught in dying phase in the distant Universe," the authors wrote.

The researchers also studied their findings alongside observations made via other ground-based telescopes. Through this, they were able to analyze the various spectral features of the radio galaxy, adding in-depth understanding about its one-of-a-kind structure.

Photo: David Metzener | Flickr

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