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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
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Neutron Stars: Billions of Times Stronger Than Steel
8 May 2009 (All day)
Talk about a hard body. New supercomputer simulations of the crusts of neutron stars--the rapidly spinning ashes left over from supernova explosions--reveal that they contain the densest and strongest material in the universe. So dense, in fact, that the gravity of the mountain-sized imperfections on the surfaces of these stars might actually jiggle spacetime itself. If so, neutron stars could offer new insights into a mysterious phenomenon known as gravity waves.
Astrophysicists already know that neutron stars are very dense. The property results from the way they form: When a giant star runs out of fuel and can no longer fight against the crushing force of its gravity, its core shrinks to the size of an asteroid, and most of its mass is blasted away in a titanic explosion called a supernova. What's left is a relic containing gigantic amounts of matter packed into a very small space that can rotate hundreds of times per second. Calculations reveal that the stars weigh as much as 90 million metric tons per teaspoon. But until now, no one has figured out the material's strength.
That's what theoretical astrophysicist Charles Horowitz and materials scientist Kai Kadau have done. Horowitz, of Indiana University in Bloomington, and Kadau, of Los Alamos National Laboratory in New Mexico, ran supercomputer simulations of how the material constituting neutron stars forms at the atomic level. Computing the effects of the star's titanic gravity on the structure of its constituent atoms, the researchers report in an upcoming issue of Physical Review Letters that the material in the star's crust is at least 10 billion times stronger than the toughest steel. It has to be, Horowitz says, to contain the immense electromagnetic forces building up within the whirring star. For example, he says, gamma-ray bursts originating from magnetars--the most highly magnetized versions of neutron stars--arise when energy buildups periodically cause the crust to rupture, in phenomena called starquakes. To hold in that much energy, Horowitz explains, their crusts must be as strong as the simulations suggest.
That incredible strength also means that when neutron stars form they can tolerate some imperfections on their surfaces. In this case, such imperfections can be mountain-sized bumps as heavy as Earth. As those bumps ride the fast-spinning stars, their mass disturbs spacetime enough to generate gravity waves, the simulations by Horowitz and Kadau show. First predicted by Albert Einstein, the waves are disruptions that radiate through the very fabric of spacetime. They travel as fast as light and can stretch every atom they encounter. Scientists have deployed new instruments in recent years in an attempt to observe the waves, but so far they have remained elusive.
The calculations by Horowitz and Kadau could change that, says physicist Benjamin Owen of Pennsylvania State University, University Park. The research shows that neutron stars "could emit a hundred times more energy in gravitational waves than we thought," he says. And that could make the waves easier to detect in the future.