Monday, 22 November 2010

What our solar system would look like to alien astronomers

Scientists have used a Nasa supercomputer to work out what our solar system would look like to alien astronomers searching for other planets.
New simulations have tracked the interactions of thousands of dust grains to how this view might have changed as our planetary system matured.
And astronomers hope that the new view could help them learn how to spot planets orbiting distant stars.
The dust originates in the Kuiper Belt, a cold-storage zone beyond Neptune where millions of icy bodies – including Pluto – orbit the Sun.
These images, produced by computer models that track the movement of icy grains, represent infrared snapshots of Kuiper Belt dust as seen by a distant observe.
Kuiper Belt objects occasionally crash into each other, and this relentless bump-and-grind produces a flurry of icy grains.
But tracking how this dust travels through the solar system is not easy because small particles are subject to a variety of forces in addition to the gravitational pull of the sun and planets.
The grains are affected by the solar wind, which works to bring dust closer to the sun, and sunlight, which can either pull dust inward or push it outward. Exactly what happens depends on the size of the grain.
‘Our new simulations also allow us to see how dust from the Kuiper Belt might have looked when the solar system was much younger,’ said Christopher Stark, Carnegie Institution for Science in Washington, D.C.
‘In effect, we can go back in time and see how the distant view of the solar system may have changed.’
‘The planets may be too dim to detect directly, but aliens studying the solar system could easily determine the presence of Neptune — its gravity carves a little gap in the dust,’ said Marc Kuchner, an astrophysicist at NASA’s Goddard Space Flight Centre, who led the study.
‘We’re hoping our models will help us spot Neptune-sized worlds around other stars.’
The models include the effects of collisions among grains. By ramping up the collision rate, the simulations show how the distant view of the solar system might have changed over its history
The particles also run into each other, and these collisions can destroy the fragile grains. A paper on the new models, which are the first to include collisions among grains, appeared in the Sept. 7 edition of The Astronomical Journal.
‘People felt that the collision calculation couldn’t be done because there are just too many of these tiny grains too keep track of,’ Kuchner said. ‘We found a way to do it, and that has opened up a whole new landscape.’
With the help of NASA’s Discover supercomputer, the researchers kept tabs on 75,000 dust particles as they interacted with the outer planets, sunlight, the solar wind — and each other.
The size of the model dust ranged from about the width of a needle’s eye to more than a thousand times smaller, similar in size to the particles in smoke.
During the simulation, the grains were placed into one of three types of orbits found in today’s Kuiper Belt at a rate based on current ideas of how quickly dust is produced.
From the resulting data, the researchers created synthetic images representing infrared views of the solar system seen from afar.
‘One thing we’ve learned is that, even in the present-day solar system, collisions play an important role in the Kuiper Belt’s structure,’ Stark said.
That’s because collisions tend to destroy large particles before they can drift too far from where they’re made. This results in a relatively dense dust ring that straddles Neptune’s orbit.

Source: dailymail

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