Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
. 24/7 Space News .

Neutron Stars' X-ray Superbursts Mystify, Inspire Los Alamos Scientists
by Staff Writers
Los Alamos NM (SPX) Dec 10, 2013

A small, dense object only 12 miles in diameter is responsible for this beautiful X-ray nebula that spans 150 light years. At the center of this image made by NASA's Chandra X-ray Observatory is a very young and powerful pulsar, known as PSR B1509-58, or B1509 for short. The pulsar is a rapidly spinning neutron star which is spewing energy out into the space around it to create complex and intriguing structures, including one that resembles a large cosmic hand. Image courtesy NASA.

Massive X-ray superbursts near the surface of neutron stars are providing a unique window into the operation of fundamental forces of nature under extreme conditions.

"Scientists are intrigued by what exactly powers these massive explosions, and understanding this would yield important insights about the fundamental forces in nature, especially on the astronomical/cosmological scale," said Peter Moller of Los Alamos National Laboratory's Theoretical Division.

A neutron star is created during the death of a giant star more massive than the sun, compressed to a tiny size but with gravitational fields exceeded only by those of black holes. And in the intense, neutron-rich environment, nuclear reactions cause strong explosions that manifest themselves as X-ray bursts and the X-ray superbursts that are more rare and 1000 times more powerful.

Los Alamos researchers and former postdocs contributed to the paper "Strong neutrino cooling by cycles of electron capture and beta decay in neutron star crusts" that was published in Nature's online edition of Dec. 1, 2013.

The importance of discovering an unknown energy source of titanic magnitude in the outermost layers of accreting neutron star surfaces is heightened by the unresolved issue of neutrino masses, the recent discovery of the Higgs boson and the fact that highly-neutron-rich nuclei with low-lying states enable "Weak Interactions," prominent in stellar explosions. (The weak nuclear force is one of four fundamental sources, such as gravity, which interacts with the neutrinos; it is responsible for some types of radioactive decay.)

These hitherto celestially operative nuclei are expected to be within the experimental reach of the Facility for Rare Isotope Beams (FRIB), a proposed user facility at Michigan State University funded by the U.S. Department of Energy Office of Science.

"The terrestrial experimental study of Weak Interactions in highly deformed, neutron-rich nuclei that FRIB can potentially provide is lent support by this ground-breaking Nature letter, since Los Alamos has been one of the few homes to theoretical studies of deformed nuclei and their role in astrophysics, and remains so to this day," said Moller, who coauthored the paper with a multidisciplinary team including former Los Alamos postdoctoral researchers Sanjib Gupta, now a faculty member at the Indian Institute of Technology (IIT), Ropar and Andrew Steiner, now a research assistant professor at INT, Seattle.

Previously a common assumption was that that the energy released in these radioactive decays would power the X-ray superburst explosions. This was based on simple models of nuclear beta-decay, sometimes postulating the same decay properties for all nuclei. It turns out, however, that it is of crucial importance to develop computer models that realistically describe the shape of each individual nuclide since they are not all spherical.

At Los Alamos scientists have carried out detailed calculations of the specific, individual beta-decay properties of thousands of nuclides, all with different decay properties, and created databases with these calculated properties.

The databases are then used at MSU as input into models that trace the decay pathways with the passage of time in accreting neutron stars and compute the total energy that is released in these reactions.

The new, unexpected result is that so much energy escapes by neutrino emission that the remaining energy released in the beta decays is not sufficient to ignite the X-ray superbursts that are observed. Thus the superbursts' origin has now become a puzzle.

Solving the puzzle will require that we calculate in detail the consequences of shapes of neutron-rich nuclei, the authors said, and it requires that they simultaneously analyze the role played by neutrinos in neutron star X-ray bursts whose energetic magnitudes are exceeded only by explosions in the nova/supernova class.

The strong nuclear deformations that formed the basis for the neutrino cooling in neutron star crusts also play a role in a number of astrophysical settings, and have been taken into account in studies of supernovae explosions and subsequent collapses, funded by Los Alamos' Laboratory Directed Research and Development (LDRD) programs.

Nuclear-structure databases valued worldwide
The large databases compiled by use of these and other nuclear-structure models are also used in several other Los Alamos programs. For example in modeling nuclear-reactor behavior, researchers have had to take into account beta-decay both because delayed neutrons are emitted, which governs the criticality of the reactor, and because it generates heat, just as in the neutron star.

Another current application is in nuclear non-proliferation programs. One method for detecting clandestine nuclear material in cargo shipments is to bombard cargoes with a small number of neutrons. If emission of delayed neutrons is detected after neutron bombardment, scientists have a sure signature of fissile nuclear material. The theoretical databases compiled at Los Alamos are not just used internally but are also part of nuclear-structure databases maintained by the International Atomic Energy Agency.

The authors on the paper are Hendrik Schatz from MSU; Sanjib Gupta from IIT Ropar; Peter Mller from LANL; Mary Beard and Michael Wiescher from the University of Notre Dame; Edward F. Brown, Alex T. Deibel, Laurens Keek, and Rita Lau from MSU; Leandro R. Gasques from the Universidade de Sao Paulo; William Raphael Hix from Oak Ridge National Laboratory and the University of Tennessee; and Andrew W. Steiner from the University of Washington.


Related Links
Los Alamos National Laboratory
Stellar Chemistry, The Universe And All Within It

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Explosive growth of young star
Copenhagen, Denmark (SPX) Dec 08, 2013
A star is formed when a large cloud of gas and dust condenses and eventually becomes so dense that it collapses into a ball of gas, where the pressure heats the matter, creating a glowing gas ball - a star is born. New research from the Niels Bohr Institute, among others, shows that a young, newly formed star in the Milky Way had such an explosive growth, that it was initially about 100 times br ... read more

Silent Orbit for China's Moon Lander

China's most moon-like place

LADEE Instruments Healthy and Ready for Science

China launches first moon rover mission

Opportunity ascending Solander Point at rim of Endeavour Crater

Rover results include first age and radiation measurements on Mars

Mars lake may have been friendly to microbes: NASA

One-way ticket to Mars: space colonists wanted!

Heat Shield for NASA's Orion Spacecraft Arrives at Kennedy Space Center

Space exploration can drive the next agricultural revolution

Global patent growth hits 18-year high

Facebook joins NYU in artificial intelligence lab

China moon rover enters lunar orbit: Xinhua

Turkey keen on space cooperation with China

China space launch debris wrecks villagers' homes: report

Designer: moon rover uses cutting-edge technology

New crew to run space station in March

Russian android may take on outer space operations at ISS

Repurposing ISS Trash for Power and Water

Russian spacecraft with advanced navigation system docks with ISS

Kazakhstan to end Proton missions in 2025

Russian Proton-M rocket launches Inmarsat-5F1 satellite

Basic build-up is being completed for Arianespace's Soyuz to launch Gaia

Third time a charm: SpaceX launches commercial satellite

Hot Jupiters Highlight Challenges in the Search for Life Beyond Earth

Astronomers find strange planet orbiting where there shouldn't be one

Hubble Traces Subtle Signals of Water on Hazy Worlds

Astronomers detect water in atmosphere of distant exoplanets

New setback for Canadian gold mine plan

Making a gem of a tiny crystal

Shortage of rare materials said holding back technology development

Goddard Planetary Instruments Score a Hat Trick

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement