Crust of neutron stars 10 billion times stronger than steel

April 15th, 2009 - 2:25 pm ICT by ANI  

London, April 15 (ANI): New simulations indicate that the crust of neutron stars is 10 billion times stronger than steel.

According to a report in New Scientist, this finding makes the surface of these ultra-dense stars tough enough to support long-lived bulges that could produce gravitational waves detectable by experiments on Earth.

Neutron stars are the cores left behind when relatively massive stars explode in supernovae. They are incredibly dense, packing about as much mass as the sun into a sphere just 20 kilometers or so across, and some rotate hundreds of times per second.

Because of their extreme gravity and rotational speed, neutron stars could potentially make large ripples in the fabric of space - but only if their surfaces contain bumps or other imperfections that would make them asymmetrical.

A number of mechanisms have been proposed to create these bumps. In theory, these bulges could be stable on the outer surface of the star.

Neutron stars are thought to be made up of a soup of neutrons covered with a solid crust. The crust is composed of crystals of neutron-rich atoms.

“But one of the big unknowns for all that work is the strength of the crust. Can you really support a mountain, or will the crust just collapse under the weight?” said Charles Horowitz of Indiana University in Bloomington.

Since laboratory experiments cannot replicate the extreme conditions on the surface of a neutron star, astronomers have largely assumed that the crust’s strength would be similar to that of the strongest substances on Earth.

But in new computer simulations, Horowitz and Kai Kadau of the Los Alamos National Laboratory show the crust of a neutron star is much stronger.

Materials like rock and steel break because their crystals have gaps and other defects that link up to create cracks. But, the enormous pressures in neutron stars squeeze out many of the imperfections.

That produces extraordinarily clean crystals that are harder to break.

A cube of neutron star crust can be deformed by 20 times more than a cube of stainless steel before breaking.

But the atoms in neutron star crusts are pulled together much more tightly than in steel, so it takes 10 billion times as much pressure to push it to the breaking point, Horowitz told New Scientist.

The stronger crust means a neutron star can support a larger bulge than thought. A “mountain” could rise some 10 centimeters above the surface, stretching over several kilometers.

That would produce gravitational waves with 100 times the energy as those previously calculated. (ANI)

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