Artist's conception of a magnetar, with magnetic field lines

A magnetar is a neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious amounts of high-energy electromagnetic radiation, particularly X-rays and gamma-rays. The theory regarding these objects was formulated by Robert Duncan and Christopher Thompson in 1992, based on a suggestion made by Jonathan Katz in 1982. In the course of the decade that followed, the magnetar hypothesis has become widely accepted as a likely physical explanation for observable objects known as soft gamma repeaters and anomalous X-ray pulsars. Image File history File links Retreived July 18, 2005 from [1] Image is from a NASA server, by a NASA employee, making them public domain, not an attribution license as the following information from the page claims: Images created by Robert S. Mallozzi using Maya, Composer, POV-Ray, Gimp, and... Image File history File links Retreived July 18, 2005 from [1] Image is from a NASA server, by a NASA employee, making them public domain, not an attribution license as the following information from the page claims: Images created by Robert S. Mallozzi using Maya, Composer, POV-Ray, Gimp, and... A neutron star is one of the few possible endpoints of stellar evolution. ... To meet Wikipedias quality standards, this article may require cleanup. ... Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Gamma rays (often denoted by the Greek letter gamma, γ) are an energetic form of electromagnetic radiation produced by radioactive decay or other nuclear or subatomic processes such as electron-positron annihilation. ... Robert Duncan is an astrophysicist at the University of Texas at Austin. ... A soft gamma repeater is an astronomical object, now known to be a type of magnetar, which emits large bursts of gamma rays and X-rays at irregular intervals. ... Anomalous X-ray Pulsars (AXPs) are now widely believed to be magnetars—young, isolated, highly magnetized neutron stars. ...

Formation

When, in a supernova, a star collapses to a neutron star, its magnetic field increases dramatically in strength (halving a linear dimension increases the magnetic field fourfold). Duncan and Thompson calculated that the magnetic field of a neutron star, normally an already enormous 10⁸ teslas could, through the dynamo mechanism, grow even larger, to more than 10¹¹ teslas (or 10¹⁵ gauss). Such a highly magnetic neutron star is called a magnetar. Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The tesla (symbol T) is the SI derived unit of magnetic flux density (or magnetic induction). ... An electrical generator is a device that converts mechanical energy to electrical energy, generally using electromagnetic induction. ... For a biography of the mathematician, see: Carl Friedrich Gauss The gauss, abbreviated as G, is the cgs unit of magnetic flux density or magnetic induction (B), named after the German mathematician and physicist Carl Friedrich Gauss. ...

The supernova might lose 10% of its mass in the explosion. In order for such large stars (10–30 solar masses) not to collapse straight into a black hole, they have to shed a larger proportion of their mass—maybe another 80%. A black hole is an object predicted by general relativity[1] with a gravitational field so strong that nothing can escape it — not even light. ...

It is estimated that about 1 in 10 supernova explosions results in a magnetar rather than a more standard neutron star or pulsar. This happens when the star already has a fast rotation and strong magnetic field before the supernova. It is thought that a magnetar's magnetic field is created as a result of a convection-driven dynamo of hot nuclear matter in the neutron star's interior that operates in the first ten seconds or so of a neutron star's life. If the neutron star is initially rotating as fast as the period of convection, about ten milliseconds(this needs a correction), then the convection currents are able to operate globally and transfer a significant amount of their kinetic energy into magnetic field strength. In slower-rotating neutron stars, the convection currents form only in local regions. Composite Optical/X-ray image of the Crab Nebula pulsar, showing surrounding nebular gases stirred by the pulsars magnetic field and radiation. ...

Short lifetime

In the outer layers of a magnetar, which consist of a plasma of heavy elements (mostly iron), tensions can arise that lead to 'starquakes'. These seismic vibrations are extremely energetic, and result in a burst of X-ray and gamma ray radiation. To astronomers, such an object is known as a soft gamma repeater. A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation A solar coronal mass ejection blasts plasma throughout the solar system. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... A starquake is an astrophysical phenomenon when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ... A soft gamma repeater is an astronomical object, now known to be a type of magnetar, which emits large bursts of gamma rays and X-rays at irregular intervals. ...

The life of a magnetar as a soft gamma repeater is short: Starquakes cause large ejections of energy, and matter. The matter is held in the strong magnetic field, and evaporates in minutes. Radial ejection of matter carries away angular momentum which slows the rotation. Magnetars lose rotational speed at a higher rate than other neutron stars, attributed to their high magnetic field. Slowdown weakens the magnetic field, and after only about 10,000 years the starquakes cease. After this, the star still radiates X-rays, and astronomers conjecture it forms an anomalous X-ray pulsar. After another 10,000 years, it becomes completely quiet. Starquakes are explosive events and some have been directly recorded, such as that at SGR 1806-20 on December 27, 2004, and more are expected to be recorded as telescopes increase in number and capability. Anomalous X-ray Pulsars (AXPs) are now widely believed to be magnetars—young, isolated, highly magnetized neutron stars. ... In astronomy, SGR 1806-20 is a magnetar, a particular type of neutron star. ... December 27 is the 361st day of the year in the Gregorian Calendar (362nd in leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Known Magnetars

• SGR 1806-20, located 50,000 light-years from Earth on the far side of our Milky Way galaxy in the constellation of Sagittarius.
• 1E 1048.1-5937, located 9,000 light-years away in the constellation Carina. The original star, out of which the magnetar formed, had a mass 30 to 40 times that of the Sun.

As of December 2004, 4 soft gamma repeaters and 5 anomalous X-ray pulsars are known, with a further four candidates in need of confirmation. In astronomy, SGR 1806-20 is a magnetar, a particular type of neutron star. ... For the astrological sign, see Sagittarius (astrology). ... Cheese wizz rulz hardcore. ... The Sun is the star of our solar system. ...

Effects of superstrong magnetic fields

A magnetic field above 10 gigateslas is strong enough to wipe a credit card from half the distance of the Moon from the Earth. A small neodymium based rare earth magnet has a field of about 1 tesla, Earth has a geomagnetic field of 30-60 microteslas, and most media used for data storage can be erased with a millitesla field at very short range. Bulk silicate composition (estimated wt%) SiO2 44. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... General Name, Symbol, Number neodymium, Nd, 60 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white, yellowish tinge Atomic mass 144. ... A rare earth is an oxide of a rare earth element. ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ...

The magnetic field of a magnetar would be lethal at a distance of up to 1000 km, tearing tissues due to the diamagnetism of water. Tidal forces of a 1.4 solar mass magnetar would also be lethal at such a distance, pulling an average-sized human apart with a force of over 20 kilonewtons (over 4500 pounds-force). km redirects here. ... Brugmans (in 1778) was the first person to observe that certain materials were repelled by magnetic fields. ... The tidal force is a secondary effect of the force of gravity and is responsible for the tides. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... The newton (symbol: N) is the SI unit of force. ... The pound-force is a non-SI unit of force or weight (properly abbreviated lbf or lbf). The pound-force is equal to a mass of one pound multiplied by the standard acceleration due to gravity on Earth (which is defined as exactly 9. ...

References

• "Origin of magnetars", CNN, 2 February 2005.
• "The Brightest Blast", Sky and Telescope, 18 February 2005.

February 2 is the 33rd day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... February 18 is the 49th day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

External links

• Recording (and animation) of XTE J1810-197.
• Creation of magnetars solved Formed when the biggest stars explode
• NASA: "Magnetar" discovery solves 19-year-old mystery Citat: "...suggested a magnetic field strength of about 800 trillion [g]auss...").
• Robert C. Duncan, University of Texas at Austin: 'Magnetars', Soft Gamma Repeaters & Very Strong Magnetic Fields
• NASA Astrophysics Data System (ADS): Duncan & Thompson, Ap.J. 392, L9) 1992
• NASA Astrophysics Data System (ADS): Katz, J. I., Ap.J. 260, 371 (1982)
• NASA ADS, 1999: Discovery of a Magnetar Associated with the Soft Gamma Repeater SGR 1900+14
• Chryssa Kouveliotou, Robert Duncan, and Christopher Thompson, "Magnetars," Scientific American, Feb. 2003, pp. 34-41 (PDF)
• Robert C. Duncan and Christopher Thompson, "Formation of Very Strongly Magnetized Neutron Stars: Implications for Gamma-Ray Bursts," Astronomical Journal, vol. 392, no. 1 (June 10, 1992), pp. L9?L13.
• Strange Pulsing Star Puzzles Astronomers - A magnetar found to emit radio waves, contrary to previous theories.