A magnetar is a type of neutron star believed to have an extremely powerful magnetic field (∼1013 to 1015G, ∼109 to 1011T). The magnetic field decay powers the emission of high-energyelectromagnetic 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 became widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs).
magnetar 是一种中子星，据信它具有非常强大的磁场（〜1013至1015 G，〜109至1011 T）。 磁场衰减为高能电磁辐射（尤其是X射线和伽马射线）的发射提供动力。 关于这些物体的理论是由罗伯特·邓肯和克里斯托弗·汤普森在1992年提出的，但是在1979年3月5日发现了第一个记录的被认为是来自磁石的伽马射线爆发。 在接下来的十年中，磁极假说被广泛接受，作为对软伽玛中继器（SGR）和异常X射线脉冲星（AXP）的可能解释。
Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter and have a mass 2–3 times that of the Sun. The density of the interior of a magnetar is such that a tablespoon 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 by rotating comparatively more quickly. Most neutron stars rotate once every one to ten seconds, whereas magnetars rotate once in less than one second. A magnetar’s 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.
像其他中子星一样，磁星的直径约为20公里（12英里），质量是太阳的2-3倍。 磁场的内部密度如此之大，一汤匙物质的质量将超过1亿吨。 磁场与其他中子星的区别在于磁场更强，旋转速度也相对更快。 大多数中子星每1到10秒旋转一次，而磁星在不到1秒的时间内旋转一次。 磁星的磁场会引起非常强烈的特征性X射线和伽马射线爆发。 磁星的有效寿命很短。 它们的强磁场在大约10,000年后衰减，此后活动和强X射线发射停止。 考虑到当今可观测到的磁星数量，据一项估算，银河系中的非活动磁星数量为3000万或更多。
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.
Magnetars are characterized by their extremely powerful magnetic fields of ∼109 to 1011 T. These magnetic fields are hundreds of millions of times stronger than any man-made magnet, and quadrillions of times more powerful than the field surrounding Earth. Earth has a geomagnetic field of 30–60 microteslas, and a neodymium-based, rare-earth magnet has a field of about 1.25 tesla, with a magnetic energy density of 4.0×105 J/m3. A magnetar’s 1010 tesla field, by contrast, has an energy density of 4.0×1025 J/m3, with an E/c2 mass density more than 10,000 times that of lead. General relativity predicts significant spacetime bending effects due to these huge magnetic fields, but quantum considerations suggest otherwise. The magnetic field of a magnetar would be lethal even at a distance of 1000 km due to the strong magnetic field distorting the electron clouds of the subject’s constituent atoms, rendering the chemistry of life impossible. At a distance of halfway from Earth to the moon, a magnetar could strip information from the magnetic stripes of all credit cards on Earth. As of 2010, they are the most powerful magnetic objects detected throughout the universe.
电磁体的特征是其强大的磁场约为109至1011T。这些磁场比任何人造磁铁都强几亿倍，比周围的磁场强四千万倍。地球的地磁场为30-60微特斯拉，钕基稀土磁体的磁场约为1.25特斯拉，磁能密度为4.0×105 J / m3。相比之下，磁石的1010特斯拉场的能量密度为4.0×1025 J / m3，E / c2质量密度是铅的10,000倍。广义相对论预测由于这些巨大的磁场会产生显着的时空弯曲效应，但量子方面的考虑则相反。由于强磁场会扭曲对象组成原子的电子云，因此即使在1000 km的距离处，磁星磁场也会具有致命性。在距地球到月球一半的距离处，一个磁星可以从地球上所有信用卡的磁条中剥离信息。截至2010年，它们是在整个宇宙中检测到的最强大的磁性物体。 
As described in the February 2003 Scientific American cover story, remarkable things happen within a magnetic field of magnetar strength. “X-ray photons readily split in two or merge. The vacuum itself is polarized, becoming strongly birefringent, like a calcite crystal. Atoms are deformed into long cylinders thinner than the quantum-relativistic de Broglie wavelength of an electron.” In a field of about 105 teslas atomic orbitals deform into rod shapes. At 1010 teslas, a hydrogen atom becomes a spindle 200 times narrower than its normal diameter.
如2003年2月《科学美国人》封面故事所述，在磁场强度的磁场内发生了许多非凡的事情。 “ X射线光子很容易分裂成两个或合并。真空本身被极化，变成强双折射，就像方解石晶体。原子变形为长圆柱体，比电子的量子相对论布罗意波长还薄。”  在约105特斯拉的场中，原子轨道变形为杆状。 在1010特斯拉时，氢原子变成比正常直径窄200倍的纺锤体。
Origins of magnetic fields
The dominant theory of the strong fields of magnetars is that it results from a magnetohydrodynamic dynamo process in the turbulent, extremely dense conducting fluid that exists before the neutron star settles into its equilibrium configuration. These fields then persist due to persistent currents in a proton-superconductor phase of matter that exists at an intermediate depth within the neutron star (where neutrons predominate by mass). A similar magnetohydrodynamic dynamo process produces even more intense transient fields during coalescence of pairs of neutron stars. But another theory is that they simply result from the collapse of stars with unusually high magnetic fields.
磁星强场的主要理论是，它是由在中子星沉降到其平衡构型之前存在的湍流，极致密的导电流体中的磁流体动力学发电机过程产生的。 这些场然后由于在质子超导体相中存在的恒流而持续存在，该相存在于中子星（其中中子以质量为主）的中间深度处。 在成对的中子星凝聚期间，类似的磁流体动力学过程会产生更强的瞬变场。 但是另一种理论是，它们仅仅是由于具有异常强磁场的恒星坍塌而产生的。
Magnetar SGR 1900+14 (center of image) showing a surrounding ring of gas 7 light-years across in infrared light, as seen by the Spitzer Space Telescope. The magnetar itself is not visible at this wavelength but has been seen in X-ray light.
斯皮策太空望远镜所观测到的磁星SGR 1900 + 14（图像中心）显示了在红外光中横跨7光年的气体环。 磁石本身在此波长下不可见，但已在X射线光中看到。
When in a supernova, a star collapses to a neutron star, and its magnetic field increases dramatically in strength. Halving a linear dimension increases the magnetic field fourfold. Duncan and Thompson calculated that when the spin, temperature and magnetic field of a newly formed neutron star falls into the right ranges, a dynamo mechanism could act, converting heat and rotational energy into magnetic energy and increasing the magnetic field, normally an already enormous 108 teslas, to more than 1011 teslas (or 1015 gauss). The result is a magnetar. It is estimated that about one in ten supernova explosions results in a magnetar rather than a more standard neutron star or pulsar.
当处于超新星状态时，恒星坍缩成中子星，其磁场强度急剧增加。 将线性尺寸减半会使磁场增加四倍。 邓肯和汤普森（Duncan and Thompson）计算得出，当新形成的中子星的自旋，温度和磁场落在正确的范围内时，发电机机制就会起作用，将热量和旋转能转化为磁能并增加磁场，通常已经是巨大的108 特斯拉，超过1011特斯拉（或1015高斯）。 结果是一个磁星。 据估计，大约有十分之一的超新星爆炸会产生一个磁星，而不是一个更标准的中子星或脉冲星。
On March 5, 1979, a few months after the successful dropping of satellites into the atmosphere of Venus, the two unmanned Soviet spaceprobes, Venera 11 and 12, that were then drifting through the Solar System were hit by a blast of gamma radiation at approximately 10:51 EST. This contact raised the radiation readings on both the probes from a normal 100 counts per second to over 200,000 counts a second, in only a fraction of a millisecond.
1979年3月5日，即成功地将卫星降落到金星大气层后的几个月，两个随即飘移通过太阳系的苏联无人太空探测器Venera 11和12被约γ辐射冲击 美国东部标准时间10:51。 这种接触使两个探头的辐射读数从正常的每秒100个计数提高到每秒超过200,000个计数，而仅需不到几毫秒的时间。
This burst of gamma rays quickly continued to spread. Eleven seconds later, Helios 2, a NASA probe, which was in orbit around the Sun, was saturated by the blast of radiation. It soon hit Venus, and the Pioneer Venus Orbiter‘s detectors were overcome by the wave. Seconds later, Earth received the wave of radiation, where the powerful output of gamma rays inundated the detectors of three U.S. Department of Defense Vela satellites, the Soviet Prognoz 7 satellite, and the Einstein Observatory. Just before the wave exited the Solar System, the blast also hit the International Sun–Earth Explorer.
伽马射线的爆发迅速继续扩散。 11秒钟后，围绕太阳运行的NASA探测器Helios 2受到了辐射冲击的浸透。 它很快击中了金星，先锋金星轨道探测器的探测器被海浪击败。 几秒钟后，地球收到了辐射波，伽马射线的强大输出淹没了美国三部美国国防部Vela卫星，苏联Prognoz 7卫星和爱因斯坦天文台的探测器。 就在海浪离开太阳系之前，爆炸还袭击了国际太阳—地球探索者号。
This extremely powerful blast of gamma radiation constituted the strongest wave of extra-solar gamma rays ever detected; it was over 100 times more intense than any known previous extra-solar burst. Because gamma rays travel at the speed of light and the time of the pulse was recorded by several distant spacecraft as well as on Earth, the source of the gamma radiation could be calculated to an accuracy of about 2 arcseconds. The direction of the source corresponded with the remnants of a star that had gone supernova around 3000 B.C.E. It was in the Large Magellanic Cloud and the source was named SGR 0525-66; the event itself was named GRB 790305b, the first observed SGR megaflare.
这种极为强大的伽马射线爆炸构成了有史以来探测到的最强的太阳外伽马射线波； 它比以前任何已知的太阳系外爆发强度高100倍以上。 因为伽马射线以光速行进并且脉冲时间是由几个遥远的航天器以及在地球上记录下来的，所以可以计算出伽马辐射源的精度约为2弧秒。 源的方向对应于公元前3000年左右超新星的恒星残留。 它位于大麦哲伦星云中，其源名为SGR 0525-66； 该事件本身被命名为GRB 790305b，这是首次观察到的SGR特大耀斑。
Artist’s impression of a gamma-ray burst and supernova powered by a magnetar 
On February 21, 2008, it was announced that NASA and researchers at McGill University had discovered a neutron star with the properties of a radio pulsar which emitted some magnetically powered bursts, like a magnetar. This suggests that magnetars are not merely a rare type of pulsar but may be a (possibly reversible) phase in the lives of some pulsars. On September 24, 2008, ESO announced what it ascertained was the first optically active magnetar-candidate yet discovered, using ESO’s Very Large Telescope. The newly discovered object was designated SWIFT J195509+261406.
2008年2月21日，美国国家航空航天局（NASA）和麦吉尔大学（McGill University）的研究人员宣布，发现了一颗具有射电脉冲星特性的中子星，该脉冲星发出了一些电磁脉冲，例如磁星。 这表明，磁星不仅是脉冲星的一种罕见类型，而且在某些脉冲星的生命中可能是（可能是可逆的）阶段。 在2008年9月24日，ESO宣布使用ESO的甚大望远镜确定是迄今发现的第一个光学活性磁候选人。 新发现的对象称为SWIFT J195509 + 261406。
On September 1, 2014, ESA released news of a magnetar close to supernova remnant Kesteven 79. Astronomers from Europe and China discovered this magnetar, named 3XMM J185246.6+003317, in 2013 by looking at images that had been taken in 2008 and 2009. In 2013, a magnetar PSR J1745-2900 was discovered, which orbits the black hole in the Sagittarius A* system. This object provides a valuable tool for studying the ionized interstellar medium toward the Galactic Center. In 2018, the result of the merger of two neutron stars was determined to be a hypermassive magnetar.
2014年9月1日，欧洲航天局发布了一条有关超新星遗迹Kesteven 79的磁星的消息。来自欧洲和中国的天文学家在2013年通过查看在2008年和2009年拍摄的图像发现了这款名为3XMM J185246.6 + 003317的磁星。 。 2013年，发现了一个磁星PSR J1745-2900，它绕着人马座A *系统的黑洞旋转。 该对象为研究朝向银河系中心的电离星际介质提供了有价值的工具。 2018年，两个中子星合并的结果被确定为超大质量的磁星。
On 27 December 2004, a burst of gamma rays from SGR 1806-20 passed through the Solar System (artist’s conception shown). The burst was so powerful that it had effects on Earth’s atmosphere, at a range of about 50,000 light years.
2004年12月27日，来自SGR 1806-20的一堆伽马射线穿过了太阳系（显示了艺术家的构想）。 爆炸是如此强大，以至于影响了大约50,000光年的地球大气层。
到了2016年5月，已经找到了23个磁星，还有6个等待确认。完整的列表已在SGR/AXP Online Catalog给出，包括：
- SGR 0525-66, in the Large Magellanic Cloud, located about 163,000 light-years from Earth, the first found (in 1979)
- SGR 1806-20, located 50,000 light-years from Earth on the far side of the Milky Way in the constellation of Sagittarius.
- SGR 1900+14, located 20,000 light-years away in the constellation Aquila. After a long period of low emissions (significant bursts only in 1979 and 1993) it became active in May–August 1998, and a burst detected on August 27, 1998 was of sufficient power to force NEAR Shoemaker to shut down to prevent damage and to saturate instruments on BeppoSAX, WIND and RXTE. On May 29, 2008, NASA’s Spitzer Space Telescope discovered a ring of matter around this magnetar. It is thought that this ring formed in the 1998 burst.
- SGR 0501+4516 was discovered on 22 August 2008.
- 1E 1048.1−5937, located 9,000 light-years away in the constellation Carina. The original star, from which the magnetar formed, had a mass 30 to 40 times that of the Sun.
- As of September 2008, ESO reports identification of an object which it has initially identified as a magnetar, SWIFT J195509+261406, originally identified by a gamma-ray burst (GRB 070610).
- CXO J164710.2-455216, located in the massive galactic cluster Westerlund 1, which formed from a star with a mass in excess of 40 solar masses.
- SWIFT J1822.3 Star-1606 discovered on 14 July 2011 by Italian and Spanish researchers of CSIC at Madrid and Catalonia. This magnetar contrary to previsions has a low external magnetic field, and it might be as young as half a million years.
- 3XMM J185246.6+003317 Discovered by international team of astronomers, looking at data from ESA’s XMM-Newton X-ray telescope.
|Magnetar found very close to the supermassive black hole, Sagittarius A*, at the center of the Milky Way galaxy|
Unusually bright supernovae are thought to result from the death of very large stars as pair-instability supernovae (or pulsational pair-instability supernovae). However, recent research by astronomers has postulated that energy released from newly formed magnetars into the surrounding supernova remnants may be responsible for some of the brightest supernovae, such as SN 2005ap and SN 2008es.
异常明亮的超新星被认为是由于超大恒星的死亡而造成的，这些恒星是对不稳定的超新星（或搏动对不稳定的超新星）。 但是，最近天文学家的研究 推测，新形成的磁星释放到周围超新星残余物中的能量可能是某些最亮的超新星的原因，例如SN 2005ap和SN 2008es。