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Thursday, November 1, 2007

Magnetic fields may stop young stars self-destructing

Magnetic fields may stop young stars self-destructing

UNLIKE human infants, newborn stars seem to have a way to stop themselves getting too hyper for their own good. When stars form from a spinning disc of gas and dust, they should spin ever faster as gravity pulls this matter in towards the centre - just as pirouetting ice skaters spin faster as they retract their arms - and so throw material back out. Yet for some reason this doesn't happen.
Now researchers have shown that a young star's magnetic field could slow the disc's overall spin by helping to get rid of the fastest-spinning material, removing it in giant perpendicular plumes. "Lots of people have seen these jets moving rapidly away from forming stars, but we never understood why they were so well-formed," says Philip Lucas at the University of Hertfordshire. The team's computer model suggests spiral-shaped magnetic fields are the most likely to form plumes

The Magnetic Fields

Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits. The magnetic field B is defined in terms of force on moving charge in the Lorentz force law. The interaction of magnetic field with charge leads to many practical applications. Magnetic field sources are essentially dipolar in nature, having a north and south magnetic pole. The SI unit for magnetic field is the Tesla, which can be seen from the magnetic part of the Lorentz force law Fmagnetic = qvB to be composed of (Newton x second)/(Coulomb x meter). A smaller magnetic field unit is the Gauss (1 Tesla = 10,000 Gauss).

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