domenica 28 giugno 2015

NASA simulation shows planet makes waves in nearby debris disk

An incredible new computer simulation by NASA shows the planet and debris disk around the nearby star Beta Pictoris in motion. 




An incredible new computer simulation by NASA shows the planet and debris disk around the nearby star Beta Pictoris in motion.
The supercomputer simulation of the planet and debris disk around Beta Pictoris shows that the planet's motion drives spiral waves throughout the disk, a phenomenon that causes collisions among the orbiting debris.
"We essentially created a virtual Beta Pictoris in the computer and watched it evolve over millions of years," said Erika Nesvold, an astrophysicist at the University of Maryland, Baltimore County, who co-developed the simulation. "This is the first full 3-D model of a debris disk where we can watch the development of asymmetric features formed by planets, like warps and eccentric rings, and also track collisions among the particles at the same time," Nesvold said.
In 1984, Beta Pictoris became the second star known to be surrounded by a bright disk of dust and debris. Located only 63 light-years away, Beta Pictoris is estimated to be 21 million years old, or less than 1% the age of our solar system.
In 2009, astronomers confirmed the existence of Beta Pictoris b, a planet with an estimated mass of about nine times Jupiter's, in the debris disk around Beta Pictoris. Travelling along a tilted and slightly elongated 20-year orbit, the planet stays about as far away from its star as Saturn does from our Sun.
Astronomers have struggled to explain various features seen in the disk, including a warp apparent at submillimetre wavelengths, an X-shaped pattern visible in scattered light, and vast clumps of carbon monoxide gas.
A common ingredient in comets, carbon monoxide molecules are destroyed by ultraviolet starlight in a few hundred years. "Our simulation suggests many of these features can be readily explained by a pair of colliding spiral waves excited in the disk by the motion and gravity of Beta Pictoris b," said Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt. Running simulations using the Discover supercomputer operated by the NASA Center for Climate Simulation at Goddard, researchers found that as the planet moves along its tilted path, it passes vertically through the disk twice each orbit.
Its gravity excites a vertical spiral wave in the disk. Debris concentrates in the crests and troughs of the waves and collides most often there, which explains the X-shaped pattern seen in the dust and may help explain the carbon monoxide clumps.


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