Astronomers believe they’ve solved the mystery of how dying stars disintegrate.
It’s been known for some time that stars like the sun end their lives with a ‘superwind’, 100 million times stronger than the solar wind, which blows for 10,000 years and removes as much as half the mass of the star.
However, the cause of this superwind has been unclear. It had been assumed that it’s driven by minute dust grains which form in the atmosphere of the star and are pushed away from it by starlight. However, this mechanism doesn’t work well in models, with the dust grains becoming too hot, and evaporating before they can be pushed out.
However, an international team has now discovered that the grains grow to much larger sizes than had previously been thought. At almost a micrometer, they behave like mirrors and reflect starlight, rather than absorbing it.
This leaves the grains cool, so that they can be pushed out without being destroyed.They’re driven at speeds of 20 thousand miles per hour, with a similar effect to a sandstorm.
“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,” says Professor Albert Zijlstra, from the University of Manchester’s Jodrell Bank Observatory.
“Our own Earth has formed from star dust. We are now a big step further in understanding this cycle of life and death.”