From Jodrell Bank: “Astronomers discover sandstorms in space”

Jodrell Bank Lovell Telescope
Lovell

Jodrell Bank Centre for Astrophysics

11 April 2012

Astronomers at The University of Manchester believe they have found the answer to the mystery of a powerful superwind which causes the death of stars.

m82
M82: Starburst Galaxy with a Superwind

Writing in Nature, the team of researchers used new techniques which allowed them to look into the atmospheres of distant, dying stars.

The team, lead by Barnaby Norris from the University of Sydney in Australia, includes scientists from the Universities of Manchester, Paris-Diderot, Oxford and Macquarie University, New South Wales. They used the Very Large Telescope in Chile, operated by the European Southern Observatory.

ESO VLT At Night
VLT at Cerro Paranal in the Atacama Desert, Chile

Stars like the Sun end their lives with a ‘superwind’, 100 million times stronger than the solar wind. This wind occurs over a period of 10,000 years, and removes as much as half the mass of the star. At the end, only a dying and fading remnant of the star will be left. The Sun will begin to throw out these gases in around five billion years. The cause of this superwind has remained a mystery. Scientists have assumed that they 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 have now discovered that the grains grow to much larger sizes than had previously been thought. The team found sizes of almost a micrometre – 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. This may be the solution to the mystery of the superwind. The large grains are driven out by the star light at speeds of 10 kilometres per second, or 20 thousand miles per hour – the speed of a rocket. The effect is similar to a sandstorm. Compared to grains of sands, the silicates in the stellar winds are still tiny.”

See the full article here.

Jodrell Bank Centre for Astrophysics comprises research activities in astronomy and astrophysics at The University of Manchester, the world leading facilities of the Jodrell Bank Observatory, the e-MERLIN/VLBI National Facility and the Project Development Office of the Square Kilometre Array.

Jodrell Bank e-Merlin

SKA Square Kilometer Array