磁星是怎么形成（什么是磁星）

In a previous article, we crushed that idea that the Universe is perfect for life. It’s not. Almost the entire Universe is a horrible and hostile place, apart from a fraction of a mostly harmless planet in a backwater corner of the Milky

在上一篇文章中，我们彻底反驳了“宇宙是生命的乐土”这一观点。的确，它并不是。整个宇宙几乎就是一个恐怖且对生命极不友好的地方，除了在银河系偏僻的角落处存在着零星几个人畜无害的星球。

While living here on Earth takes about 80 years to kill you, there are other places in the Universe at the very other end of the spectrum. Places that would kill you in a fraction of a fraction of a second. And nothing is more lethal than supernovae and remnants they leave behind: neutron stars.

虽然在地球上你可以活到长达80岁才最终死去，但宇宙中的其他地方往往会是另一个极端。那些地方会在瞬间就将你杀死。而其中最具杀伤力的就是超新星以及超新星爆炸后留下的残余——中子星。

We’ve done a few articles about neutron stars and their different flavours, so there should be some familiar terrain here.

关于中子星以及它们的不同变种，我们已经写了一些文章，所以这里我们应该对其已有所了解。

Artist concept of a neutron star. Credit: NASA

中子星的概念图。来源：NASA

As you know, neutron stars are formed when stars more massive than our Sun explode as supernovae. When these stars die, they no longer have the light pressure pushing outward to counteract the massive gravity pulling inward.

如你所知，当比我们太阳更大的恒星发生超新星爆炸后，它就有可能形成中子星。而当这些恒星死亡，他们向外对光线的压力将无法抵消光线受到的向内的强大引力。

This enormous inward force is so strong that it overcomes the repulsive force that keeps atoms from collapsing. Protons and electrons are forced into the same space, becoming neutrons. The whole thing is just made of neutrons. Did the star have hydrogen, helium, carbon and iron before? That’s too bad, because now it’s all neutrons.

这种巨大的向内的力十分强大，超过了原子内部粒子间的斥力，以致于原子发生塌缩，使得质子和电子被强行压缩到一起，成为中子。这就是中子产生的过程。这颗恒星以前还有氢，氦，碳和铁？呵呵，现在它只有中子。

You get pulsars when neutron stars first form. When all that former star is compressed into a teeny tiny package. The conservation of angular motion spins the star up to tremendous velocities, sometimes hundreds of times a second.

刚形成的中子星首先会是一颗脉冲星。当原恒星的质量都被压缩进一个极小的空间，角动量守恒使得其产生非常高的自转速率，有时每秒可转动上百次。

But when neutron stars form, about one in ten does something really really strange, becoming one of the most mysterious and terrifying objects in the Universe. They become magnetars. You’ve probably heard the name, but what are they?

接下来，大约有十分之一的中子星在形成后会变得十分奇怪，它们是宇宙中最神秘和恐怖的物体之一。而这就是磁星。 可能你已听说过这个名字，但它们究竟是什么？

As I said, magnetars are neutron stars, formed from supernovae. But something unusual happens as they form, spinning up their magnetic field to an intense level. In fact, astronomers aren’t exactly sure what happens to make them so strong.

如上所述，磁星是由超新星形成的中子星。但与其他中子星不同的是，在它们形成后，高速的旋转使得其磁场达到一个十分强大的水平。事实上，天文学家并不确定到底发生了什么以至于磁场如此强烈。

This artist’s impression shows the magnetar in the very rich and young star cluster Westerlund 1. Credit: ESO/L. Calçada

这张概念图展示了年轻的Westerlund 1星团中的磁星，该星团存在着大量的恒星。 来源：ESO / L. Calçada

One idea is that if you get the spin, temperature and magnetic field of a neutron star into a perfect sweet spot, it sets off a dynamo mechanism that amplifies the magnetic field by a factor of a thousand.

一种观点认为，如果一颗中子星的旋转，温度和磁场能够完美的结合在一起，那么它会像发电机一样将磁场放大一千倍。

But a more recent discovery gives a tantalizing clue for how they form. Astronomers discovered a rogue magnetar on an escape trajectory out of the Milky Way. We’ve seen stars like this, and they’re ejected when one star in a binary system detonates as a supernova. In other words, this magnetar used to be part of a binary pair.

而最近的发现在解释磁星如何形成方面提供了一个可循的线索。天文学家在银河系的逃逸轨道上发现了一颗行为异常的磁星。我们以前也发现过类似的星星，他们由于双子星系统中的某一颗恒星发生超新星爆炸而被弹射出去。换句话说，这颗磁星曾是双子星系统中的一部分。

And while they were partners, the two stars orbited one another closer than the Earth orbits the Sun. This close, they could transfer material back and forth. The larger star began to die first, puffing out and transferring material to the smaller star. This increased mass spun the smaller star up to the point that it grew larger and spewed material back at the first star.

他们成对出现时，两颗恒星彼此环绕的轨道要更近于地球环绕太阳的轨道，从而他们可以来回转移物质。首先体形较大的恒星先行死去，膨胀并将物质转移给体形较小的恒星。而随着质量的增加体形较小的恒星越转越快，直到体形变大并将物质吐回给第一颗恒星。

The initially smaller star detonated as a supernova first, ejecting the other star into this escape trajectory, and then the second went off, but instead of forming a regular neutron star, all these binary interactions turned it into a magnetar. There you go, mystery maybe solved?

原体形较小的恒星发生超新星爆炸，爆炸将另一颗恒星弹射入这个逃逸轨道，然后第二颗恒星爆炸，但并未生成一颗普通的中子星，而是因双子星系统中一系列的相互作用变成了一颗磁星。但奥秘就这样被揭示了吗？

The strength of the magnetic field around a magnetar completely boggles the imagination. The magnetic field of the Earth’s core is about 25 gauss, and here on the surface, we experience less than half a gauss. A regular bar magnet is about 100 gauss. Just a regular neutron star has a magnetic field of a trillion gauss. Magnetars are 1,000 times more powerful than that, with a magnetic field of a quadrillion gauss.

人们完全难以想象磁星周围的磁场强度。在地球上，地心的磁场强度大约在25高斯，而在地表上我们只能体验不到半高斯的磁场强度。一根普通的磁铁棒的磁场强度大概是100高斯。仅一颗普通的中子星磁场强度可达1万亿高斯。而磁星的磁场比普通的中子星还要强上1000倍，也就是一千万亿高斯。

What if you could get close to a magnetar? Well, within about 1,000 kilometers of a magnetar, the magnetic field is so strong it messes with the electrons in your atoms. You would literally be torn apart at an atomic level. Even the atoms themselves are deformed into rod-like shapes, no longer usable by your precious life’s chemistry.

假如你能接近磁星，那么在大约1000公里之外，强大的磁场会干扰你原子内的电子。而你会在原子的层面直接被撕裂。甚至原子自身也会变形成棒状。无法再为你生命宝贵的化学分子所用。

But you wouldn’t notice because you’d already be dead from the intense radiation streaming from the magnetar, and all the lethal particles orbiting the star and trapped in its magnetic field.

当然这一切你都不会察觉的到，因为你早已被磁星强大的辐射流杀死。这些致命的粒子环绕在这颗星星的周围并被其强大的磁场困住无法逃脱。

Artist's conception of a starquake cracking the surface of a neutron star. Credit: Darlene McElroy of LANL

中子星表面因星震而裂开的概念图。来源：洛斯阿拉莫斯国家实验室(Los Alamos National Laboratory)的Darlene McElroy

One of the most fascinating aspects of magnetars is how they can have starquakes. You know, earthquakes, but on stars… starquakes. When neutron stars form, they can have a delicious murder crust on the outside, surrounding the degenerate death matter inside. This crust of neutrons can crack, like the tectonic plates on Earth. As this happens, the magnetar releases a blast of radiation that we can see clear across the Milky Way.

关于磁星最迷人的现象之一是，它们怎么会有星震。地震大家都知道，但星星...... 星震。当中子星形成后，它们的表面虽然是一个优雅的谋杀工具，但体内的物质却会给自身带来死亡。中子星的表面就像地球的板块一样会裂开。当其裂开时，我们能明确的观察到磁星在银行系中释放出来的辐射冲击。

In fact, the most powerful starquake ever recorded came from a magnetar called SGR 1806-20, located about 50,000 light years away. In a tenth of a second, one of these starquakes released more energy than the Sun gives off in 100,000 years. And this wasn’t even a supernova, it was merely a crack on the magnetar’s surface.

事实上，有史以来最强大的星震来自一个名为SGR 1806-20磁星，它位于约50000光年之外。在十分之一秒内，一次星震释放的能量比太阳在10万年放出还要高。而这不是来自一颗超新星，它仅仅是来自磁星表面产生的裂纹。

Magnetars are awesome, and provide the absolute opposite end of the spectrum for a safe and habitable Universe. Fortunately, they’re really far away and you won’t have to worry about them ever getting close.

令人畏惧的磁星是安全和适宜居住宇宙的另一个极端。幸运的是，他们真的很远，所以你不用担心他们会跟我们越来越接近。(本文由 杨乃漳 翻译)