Longest intergalactic beam discovered

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London, Dec 8: A team of Indian astronomers have discovered the longest intergalactic beam, stretching for more than a million light years, that might help to reveal how such jets of matter bind themselves together.

The discovery emerged from a large elliptical galaxy called CGCG 049-033, which is about 600 million light years away. A team led by Joydeep Bagchi of Pune University in Maharashtra, India, noticed emission from this galaxy during a broad search for radio sources, and then took a closer look using the Giant Metrewave Radio Telescope near Pune and the 100-metre Effelsberg radio dish in Germany.

The jet they saw is nearly 1.5 million light years long, twice the length of the previous record holder. It also has an unusual characteristic not observed in other jets.

Jets usually come in fairly well matched pairs, pointing in opposite directions. The new jet's counterpart, however, appears much shorter. That could be because the apparently shorter jet is pointing away from us; so light from its far end might not have had time to reach us yet.

Jets are seen all over the cosmos squirting out of many different types of object, including stars that are just beginning to form. The most powerful ones come from the cores of active galaxies, where gas falling towards a giant black hole generates a mixture of heat, high-energy particles and magnetic fields.

Interestingly, the radio waves emitted by the newly discovered jet are strongly polarised, revealing a powerful magnetic field wrapped around the jet. "I was very surprised to find such a strong and regular magnetic field," team member Marita Krause of the University of Bonn in Germany told New Scientist.

It may be that the magnetic field acts as a containing sheath, preventing the high-pressure gas in the jet from dispersing. That could explain why this jet is so long. A somewhat weaker version of this magnetic containment field might help hold jets together around other types of astronomical objects.

The research team plans to get an even more detailed picture of the jet and its magnetic fields using the Very Large Array radio observatory in New Mexico, US.




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