How magnetic forces create knots in stars jets

February 10th, 2009 - 4:28 pm ICT by ANI  

Washington, Feb 10 (ANI): Scientists at Rochester University have performed the first laboratory experiment to explain how jets of matter streaming out of stars achieve their mysterious knotted shapes through magnetic forces.

The predominant theory says that jets are essentially fire hoses that shoot out matter in a steady stream, and the stream breaks up as it collides with gas and dust in space. But, that doesnt appear to be so after all, said Adam Frank, professor of astrophysics at the University of Rochester, and co-author of the paper.

The experiments strongly suggest that the jets are fired out more like bullets or buckshot. They dont break into piecesthey are formed in pieces, he explained.

According to Frank, the experiment, conducted by Professor Sergey Lebedevs team in the Department of Physics at Imperial College London, may be the best astrophysical experiment thats ever been done.

Replicating the physics of a star in a laboratory is exceptionally difficult, but the Imperial experiment matches the known physics of stellar jets surprisingly well, he said.

At Imperial, Lebedev sent a high-powered pulse of energy into an aluminum disk. In less than a few billions of a second, the aluminum began to evaporate, creating a cloud of plasma very similar to the plasma cloud surrounding a young star.

Where the energy flowed into the center of the disk, the aluminum eroded completely, creating a hole through which a magnetic field from beneath the disk could penetrate.

The field initially pushes aside the plasma, forming a bubble within it, who carried out the astrophysical analysis of the experiment, said Frank.

As the field penetrates further and the bubble grows, however, the magnetic fields begin to warp and twist, creating a knot in the jet. Almost immediately, a new magnetic bubble forms inside the base of the first as the first is propelled away, and the process repeats, he added.

We can see these beautiful jets in space, but we have no way to see what the magnetic fields look like, said Frank.

I cant go out and stick probes in a star, but here we can get some ideaand it looks like the field is a weird, tangled mess, he added.

According to Frank, other aspects of the experiment, such as the way in which the jets radiatively cool the plasma in the same way jets radiatively cool their parent stars, make the series of experiments an important tool for studying stellar jets.

With this new model, astrophysicists do not have to assume that the knotted jets they see in nature mean some unknown phenomenon interrupted the jets flow of material, he said. (ANI)

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