Powerful Superwinds Generate Space Sandstorms That Erode Stars
Posted on May 4, 2012
Researchers using the Very Large Telescope in Chile say they have found the answer to the mystery of a powerful space superwind that destroys stars. Stars end their lives with a superwind, which is 100 million times stronger than the solar wind. This superwind occurs over a period of 10,000 years and removes as much as half the mass of the star. Our Sun will also die in this manner in about five billion years unless our far off future selves somehow engineer a clever way to stop it.
Scientists have long assumed that these winds are driven by minute dust grains, which form in the atmosphere of the star and absorb its light. The star light pushes the dust grains (silicates) away from the star. However, models have shown that this mechanism does not work well. The dust grains become too hot, and evaporate before they can be pushed out.
The scientists discovered that the dust grains grow to much larger sizes than had previously been thought. The team found sizes of almost a micrometer - as small as dust, but huge for stellar winds. Grains of this size behave like mirrors, and reflect starlight, rather than absorbing it. This leaves the grains cool, and the star light can push them out without destroying them. The large grains are driven out by the star light at speeds of 20 thousand miles per hour. The effect is similar to a sandstorm.
Professor Albert Zijlstra, from The University of Manchester's Jodrell Bank Observatory, says, "The dust and sand in the superwind will survive the star, and later become part of the clouds in space from which new stars form. The sand grains at that time become the building blocks of planets. Our own Earth has formed from star dust. We are now a big step further in understanding this cycle of life and death."
The research team was lead by Barnaby Norris from the University of Sydney in Australia. It included scientists from the Universities of Manchester, Paris-Diderot, Oxford and Macquarie University, New South Wales.
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