MAGNETAR by MagikUnicorn

Bryce • Space • posted on Dec 18, 2013

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Description

MAGNETAR A magnetar is a type of neutron star with an extremely powerful magnetic field. The magnetic field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays. The theory regarding these objects was proposed by Robert Duncan and Christopher Thompson in 1992, but the first recorded burst of gamma rays thought to have been from a magnetar had been detected on March 5, 1979. During the following decade, the magnetar hypothesis has become widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). A recent progress in theory suggests that the energy deposition from these magnetars into the expanding supernova remnant could possibly explain few observed cases of unusually bright supernovae. Traditionally such bright events are thought to come from very large stars when they become pair-instability supernova (or pulsational pair-instability supernova). However, two papers published in 2010 by astrophysicists at the University of California Berkeley, Santa Cruz and Santa Barbara provided semi-analytical and numerical models to explain some of the brightest events ever seen, such as SN 2005ap and SN 2008es. A research led by Matt Nicholl, of the Astrophysics Research Centre at Queen's School of Mathematics and Physics of Queen's University Belfast, the results of which were published on Oct 17, 2013 in Nature, has explained the newly discovered luminous transient PTF 12dam through the same mechanism. Like other neutron stars, magnetars are around 20 kilometres (10 mi) in diameter and have a greater mass than the Sun. The density of the interior of a magnetar is such that a thimble full of its substance would have a mass of over 100 million tons. Magnetars are differentiated from other neutron stars by having even stronger magnetic fields, and rotating comparatively slowly, with most magnetars completing a rotation once every one to ten seconds, compared to less than one second for a typical neutron star. This magnetic field gives rise to very strong and characteristic bursts of X-rays and gamma rays. The active life of a magnetar is short. Their strong magnetic fields decay after about 10,000 years, after which activity and strong X-ray emission cease. Given the number of magnetars observable today, one estimate puts the number of inactive magnetars in the Milky Way at 30 million or more. Starquakes triggered on the surface of the magnetar disturb the magnetic field which encompasses it, often leading to extremely powerful gamma ray flare emissions which have been recorded on Earth in 1979, 1998, and 2004.

Comments (31)

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MagikUnicorn Online Now!

5:28PM | Wed, 18 December 2013

Magnétar Un magnétar est une étoile à neutrons disposant d'un champ magnétique extrêmement intense, qui émet des radiations électromagnétiques de haute énergie, comme les rayons X et gamma. Robert Duncan et Christopher Thompson postulèrent leur existence en 1992, et dans la décennie qui suivit elle fut acceptée comme explication plausible pour les sursauteurs gamma mous et les pulsars X anormaux. Lorsqu'une supernova devient une étoile à neutrons, l'intensité de son champ magnétique croît. Duncan et Thompson calculèrent que celui-ci, normalement déjà de 108 teslas, pouvait dépasser dans certaines conditions 1011 teslas. Une telle étoile magnétique est alors nommée magnétar. Des tensions provoquant des tremblements d'étoile se produisent parfois dans les couches externes des magnétars, constituées de plasma d'éléments lourds (principalement de fer). Ces vibrations très énergétiques produisent des bouffées de rayons X et gamma. Une telle étoile est nommée soft gamma repeater (SGR), soit sursauteur gamma mou. Il est estimé qu'une supernova sur dix donne naissance à un magnétar plutôt qu'à une étoile à neutrons ou à un pulsar. Les prérequis sont une rotation rapide et un champ magnétique intense avant explosion. Ce champ magnétique serait créé par un générateur électrique utilisant la convection de matière nucléaire durant les dix premières secondes environ de la vie d'une étoile à neutrons. Si cette dernière tourne suffisamment rapidement, les courants de convection deviennent globaux et transfèrent leur énergie au champ magnétique. Lorsque la rotation est trop lente, les courants de convection ne se forment que dans des régions locales. Les magnétars ont un champ magnétique bien supérieur à 10 gigateslas. Cette puissance est suffisante pour démagnétiser (et donc rendre inutilisable) toutes les cartes de crédit de la Terre depuis une distance égale à la moitié de celle de la Lune, et est fatale à une distance de 1000 km1. En comparaison, le champ magnétique naturel de la Terre est de 50 microteslas.

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barryjeffer

5:51PM | Wed, 18 December 2013

Spectacular as ever!! Brilliant

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Cyve

6:00PM | Wed, 18 December 2013

Merci pour toutes ces information mon ami... SUperbe creation egalement!!!

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mgtcs

6:11PM | Wed, 18 December 2013

Amazing image Magik, thank you for the informations!

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Savage_dragon

7:33PM | Wed, 18 December 2013

On a star far far away......

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magnus073

7:37PM | Wed, 18 December 2013

Magik, il s'agit d'une présentation merveilleuse. J'ai apprécié l'apprentissage de la (Magnetar) et de voir l'image que vous avez créé pour le représenter. Visite de votre galerie est éducative et agréable.

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sharky_

7:58PM | Wed, 18 December 2013

Kind of reminds me of when I was up on Mauna Kea. I had turned on my gps, set it on the truck. Before I even moved, its reading said I moved about 15 feet. It was just weird. Then one of the rangers said they had asked one of the guys that worked up at the observatory why their gps went haywire. They said it was the high magnetic field on the mountain causing errors.... Aloha

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