Visit Indian Travel Sites
Goa,
Kerala,
Tamil Nadu,
Andhra Pradesh,
Delhi,
Rajasthan,
Uttar Pradesh,
Himachal Pradesh,
Assam,
Sikkim,
Madhya Pradesh,
Jammu & Kashmir
Karnataka
|
Sandstorms in space discovered | Using new techniques, researchers have explored the atmospheres of distant, dying stars. The team, led
by Barnaby Norris from the University of Sydney in Australia used the Very Large Telescope in Chile, operated by the European Southern Observatory. At the resolution
used by the scientists including those from the Universities of Manchester, Paris-Diderot,
Oxford and Macquarie University , New South Wales , one could, from the UK , distinguish
the two headlights on a car in Australia . This extreme resolution made it possible
to resolve the red giant stars, and to see winds of gas and dust coming off the
star. 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 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. 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. Professor Albert Zijlstra, from The University of Manchester’s Jodrell
Bank Observatory, said the breakthrough changes our view of these superwinds.
For the first time, we begin to understand how the superwinds work, and how stars
(including, in the distant future, our Sun) die. “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,” he added. The study has been published in Nature. |
|
|
|
|
|