Archive for June 17, 2013

The University Of Alicante Finds The First Evidence Of A New Phase In Neutron Stars

A study led by the University of Alicante, in which in the National Research Council (CSIC) has participated, has detected what may be the first observational evidence of existence of a new exotic phase of matter in the inner crust of neutron stars (pulsars).

The latest issue of Nature Physics shows the results of a research project that addresses one of the unknowns in the field of X-ray pulsars, the existence of a limit higher than 12 seconds in the rotation periods of isolated neutron stars. This limit is actually due to the existence of new exotic phases of matter. Pulsars are neutron stars (ultracompact and strongly magnetized stars) in rotation, which emit electromagnetic radiation with amazing precision in their periodicity.

As José A. Pons says, lecturer at the University of Alicante’s Relativistic Astrophysics Group and Director of the Department of Applied Physics, who led the work: “This may be the first observational evidence of existence of the phase of nuclear ‘pasta’ inside neutron stars, which may allow that future missions of X-ray observatories can be used to define aspects of how nuclear interaction works, which is not yet entirely clear”.

Nuclear Pasta, named for its resemblance to the Italian pasta, occurs when the combination of nuclear and electromagnetic forces, at densities close to the atomic nuclei, favours the ordering of the nucleons (protons and neutrons) in non-spherical shapes , as sheets or filaments (lasagna or spaghetti).

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The Flare Star WX UMa Becomes 15 Times Brighter In Less Than 3 Minutes

A flare star. Credit: Casey Reed/NASA

A flare star. Credit: Casey Reed/NASA

Astrophysicists at the University of Santiago de Compostela (Spain) and the Byurakan Observatory (Armenia) have detected a star of low luminosity which within a matter of moments gave off a flare so strong that it became almost 15 times brighter. The star in question is the flare star WX UMa.

“We recorded a strong flare of the star WX UMa, which became almost 15 times brighter in a matter of 160 seconds,” explains to SINC the astrophysicist Vakhtang Tamazian, professor at the University of Santiago de Compostela. The finding has been published in the Astrophysics journal.

This star is in the Ursa Major constellation, around 15.6 light years from the Earth, and it forms part of a binary system. Its companion shines almost 100 times brighter, except at times such as that observed, in which the WX UMa gives off its flares. This can happen several times a year, but not as strongly as that which was recorded in this instance.

Dr Tamazian and other researchers detected this exceptional brightness from the Byurakan Observatory in Armenia. “Furthermore, during this period of less than three minutes the star underwent an abrupt change from spectral type M to B; in other words, it went from a temperature of 2,800 kelvin (K) to six or seven times more than that.”

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NASA-Led Study Explains Decades Of Black Hole Observations

A new study by astronomers at NASA, Johns Hopkins University and the Rochester Institute of Technology confirms long-held suspicions about how stellar-mass black holes produce their highest-energy light.

“Our work traces the complex motions, particle interactions and turbulent magnetic fields in billion-degree gas on the threshold of a black hole, one of the most extreme physical environments in the universe,” said lead researcher Jeremy Schnittman, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

By analyzing a supercomputer simulation of gas flowing into a black hole, the team finds they can reproduce a range of important X-ray features long observed in active black holes.

Gas falling toward a black hole initially orbits around it and then accumulates into a flattened disk. The gas stored in this disk gradually spirals inward and becomes greatly compressed and heated as it nears the center. Ultimately reaching temperatures up to 20 million degrees Fahrenheit (12 million C) — some 2,000 times hotter than the sun’s surface — the gas shines brightly in low-energy, or soft, X-rays.

For more than 40 years, however, observations have shown that black holes also produce considerable amounts of “hard” X-rays, light with energy tens to hundreds of times greater than soft X-rays. This higher-energy light implies the presence of correspondingly hotter gas, with temperatures reaching billions of degrees.

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