Studying the 'mountains' and 'starquakes' that develop on neutron stars

May 26, 2009 By Miranda Marquit feature

(PhysOrg.com) -- Neutron stars have the potential to play an important role in understanding some of the mysteries of the universe. One of factors that could help lead to an understanding of gravitational waves and the mechanisms involved in giant flares in magnetars is the strength of the crust that forms on the outside of a neutron star. In an effort to better understand the neutron star crusts, Charles Horowitz, at Indiana University in Bloomington, and his colleague Kai Kadau, at Los Alamos National Laboratory in New Mexico, have used molecular dynamics to model neutron stars and come up with improved estimates of the breaking strain.

“In 2004, a giant flare was detected coming from a magnetar. It had a huge amount of energy.” Horowitz tells PhysOrg.com. (A magnetar is a neutron star with a very powerful magnetic field.) “We think that this mechanism only makes sense if the crust is really, really strong. Such a large flare should only be possible if, by the time the crust broke, there was tremendous energy stored in the crust and magnetic field.” Horowitz hopes that the simulations run with Kadau will help shed more light on the workings of , and even perhaps answer other questions about the universe. Their work is presented in Physical Review Letters: “Breaking Strain of Neutron Star Crust and Gravitational Waves.”

Horowitz says that for many years, scientists have been studying neutron stars and the “mountains” that develop on them. The bulges that create gravitational waves are the results of temperature-dependent nuclear reactions near hot spots. “People have wondered how big they can get, how massive they could become before the crust breaks because of forces from the strong ,” he explains. It is this that releases the flares that are sometimes detected.

There are two main aims for studying the possibilities for the crust of a neutron star: Learning more about these stars - what the crust is made of and how they might function - and using neutron stars as a way to possibly detect gravitational waves. Horowitz and Kadau’s model might be able to help in both of these areas, since it offers a more detailed look at what goes on when a mountain is formed - and when it collapses, causing a “starquake.”

In the first case, the simulation Horowitz and Kadau is working with shows that the crust is likely made up of ions. “It’s more or less composed of normal atoms,” Horowitz explains, “but they’ve been ionized. The huge pressure of the star squeezes the electrons in such a way as to create ions. We think that the material is slightly heavier than iron, possibly selenium.”

Understanding neutron star mechanisms, however, may also help scientists find gravitational waves. “The mountains that form on these rapidly rotating neutron stars generate gravitational waves quite efficiently. If we understand how this works, we might be able to make better predictions of which neutron stars would be most likely to produce the strongest gravitational waves. It would give scientists a better place to look.”

Horowitz explains that gravitational waves are curves in space-time, predicted by Einstein’s theory of general relativity. “To actually find these waves would be a major discovery and a confirmation of general relativity. And I think our model can help in that aim.”

More information: C.J. Horowitz, Kai Kadau. “Breaking Strain of Neutron Star Crust and ,” Physical Review Letters (2009). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.102.191102 .

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: The unifying framework of symmetry reveals properties of a broad range of physical systems

add to favorites email to friend print save as pdf

Related Stories

New-School 'Aether' May Shed Light on Neutron Stars

Oct 10, 2007

Among scientists, it is widely believed that there is no such thing as an aether – a medium pervading all space that allows light waves to propagate, similar to how sound needs air or water – but a part of its spirit ...

Starquake Reveals Hidden Structure of a Neutron Star

Apr 27, 2006

A US-German team of scientists from the Max Planck Institute for Astrophysics and NASA have used NASA's Rossi X-ray Timing Explorer to estimate the depth of the crust on a neutron star, the densest object known ...

Catching the Gravitational Wave

Jul 17, 2007

For nearly a century, scientists searched to uncover the tremors Einstein believed were produced by waves in the fabric of space and time.

Recommended for you

What time is it in the universe?

Aug 29, 2014

Flavor Flav knows what time it is. At least he does for Flavor Flav. Even with all his moving and accelerating, with the planet, the solar system, getting on planes, taking elevators, and perhaps even some ...

Watching the structure of glass under pressure

Aug 28, 2014

Glass has many applications that call for different properties, such as resistance to thermal shock or to chemically harsh environments. Glassmakers commonly use additives such as boron oxide to tweak these ...

Inter-dependent networks stress test

Aug 28, 2014

Energy production systems are good examples of complex systems. Their infrastructure equipment requires ancillary sub-systems structured like a network—including water for cooling, transport to supply fuel, and ICT systems ...

Explainer: How does our sun shine?

Aug 28, 2014

What makes our sun shine has been a mystery for most of human history. Given our sun is a star and stars are suns, explaining the source of the sun's energy would help us understand why stars shine. ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

brant
1.3 / 5 (3) May 26, 2009
"Such a large flare should only be possible if, by the time the crust broke, there was tremendous energy stored in the crust and magnetic field."

What a crock of neutronium!!!