New findings could help advance understanding of matter at extreme densities
Neutron stars, the extraordinarily dense stellar bodies created when massive stars collapse, are known to host the strongest magnetic fields in the universe -- as much as a billion times more powerful than any man-made electromagnet. But some neutron stars are much more strongly magnetized than others, and this disparity has long puzzled astrophysicists.
Now, a study by McGill University physicists Konstantinos Gourgouliatos and Andrew Cumming sheds new light on the expected geometry of the magnetic field in neutron stars. The findings, published online April 29 in Physical Review Letters, could help scientists measure the mass and radius of these unusual stellar bodies, and thereby gain insights into the physics of matter at extreme densities.
Some previous theoretical studies have suggested that the magnetic field of a neutron star should break into smaller loops and dissipate as the star ages – a phenomenon known as “turbulent cascade.” Yet, there are several “middle-aged” neutron stars (roughly one million to a few million years old) that are known to have relatively strong magnetic fields, leaving scientists at a loss to reconcile the theoretical models with actual observations.
To better understand how the magnetic field changes as a neutron star ages, Gourgouliatos and Cumming ran a series of computer simulations. These showed the magnetic field evolving rapidly at first, in line with previous predictions. But then the evolution took a surprising turn: in all the simulations, no matter what the magnetic field looked like when the neutron star was born, the field took on a particular structure and its evolution dramatically slowed.
“A cascade in a magnetic field is akin to what happens when you add cream to your coffee and stir it: the cream rapidly gets broken up into pieces and mixes into the coffee,” Cumming explains. “The original prediction was that neutron star crusts would do the same to their magnetic fields; so if you could walk around on the surface with a compass trying to walk towards magnetic north, you would end up walking around in random directions. Instead, we find in these new simulations that the magnetic field actually remains quite simple in structure – as if the cream refused to mix into the coffee – and you could, indeed, use a compass to navigate around on the surface of the star.”
The McGill researchers call this final magnetic-field configuration the “Hall attractor” state, after the so-called Hall effect, which is thought by astrophysicists to drive magnetic field evolution in neutron-star crusts. “This result is also significant because it shows that the Hall effect, a phenomenon first discovered in terrestrial materials and which is thought to help weaken a magnetic field through turbulence, can actually lead to an attractor state with a stable magnetic-field structure,” Gourgouliatos says.
The research was supported by the Centre de Recherche en Astrophysique du Québec and the Natural Sciences and Engineering Research Council of Canada.
“Hall Attractor in Axially Symmetric Magnetic Fields in Neutron Star Crusts”, Konstantinos N. Gourgouliatos and Andrew Cumming, Physical Review Letters, published 29 April 2014.
Chris Chipello | idw - Informationsdienst Wissenschaft
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Life Sciences
27.04.2017 | Physics and Astronomy
27.04.2017 | Earth Sciences