Saturday, December 08, 2007

A Million Light Years

An intergalactic particle beam stretching for more than a million light years is the longest ever seen. According to the team that discovered this record breaker, it could help reveal how such jets of matter bind themselves together.

Jets are seen all over the cosmos emerging 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. In some cases, these elements combine to spit out narrow columns of hot gas laced with high-energy particles, which drill though the galaxy and on out into space.

The latest discovery emerges 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. If this jet sprang instead from the centre of the Milky Way, it would loom over us like a skyscraper and would stretch halfway to the Andromeda galaxy.

It is unusual in other ways too. 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.

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," said team member Marita Krause from the University of Bonn in Germany.

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 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.
The Evolution of Binary Stars from News Account @ Scientific Blogging
When Do Gas Giants Reach The Point Of No Return? from Science Daily
Odd Little Star Has Magnetic Personality from the Gemini Observatory

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