Constraining compact binary formation with gravitational wave observations

黑洞和中子星是宇宙中最奇怪的物体，它们的质量比太阳还大，但直径只有几公里。它们是由大质量恒星的残骸形成的，这些恒星迅速燃烧燃料，以超新星爆炸的形式结束生命，其亮度超过整个星系。不同类型的恒星有不同类型的超新星：它们的质量、旋转和组成都在决定它们的最终命运方面发挥着作用，尽管细节还没有完全了解。超新星爆炸后剩下的是一个密度如此之大的物体，它的引力扭曲了它周围的时空：中子星被认为含有密度最大的物质，比原子核还要大，而原子核是唯一一种足够强大的物质，可以支撑恒星抵抗自身的引力。更极端的是黑洞，当恒星的质量更大时就会形成黑洞，而中子星的物质无法支撑它的重量。当这种情况发生时，恒星坍缩成一个黑洞，变得如此致密，以至于连光都无法逃脱引力的牵引。在这一点上，视界形成，将其内容隐藏在宇宙的其余部分。由于黑洞不发光，所以天文学家不可能发现它们，除非它们正在积极地从伴星中吸积物质。但还有另一种方法可以探测它们，使用一种全新的天文学工具：引力波。根据爱因斯坦的广义相对论，当黑洞和中子星在一个双星系统中被发现时，如此多的物质在如此集中的空间中运动，会在时空本身产生振动。它们以光速穿越宇宙，改变了它们所经过的一切事物的尺寸，但肉眼是看不见的。在地球上，物理学家长期以来一直在通过使用引力波探测器进行极其精确的距离测量来寻找引力波。到目前为止还没有发现任何迹象，但很快，先进的LIGO和先进的处女座探测器将投入使用，它们的灵敏度应该能让我们探测到距离地球数亿光年以内的双中子星发出的引力波，甚至能探测到更远的、更重的双黑洞。这些探测器非常灵敏，它们所能测量的变化相当于太阳和土星之间的距离改变了一根发丝的宽度。在引力波中编码的是有关发射它们的源的信息，这将使我们了解中子星和黑洞的质量和旋转。通过测量许多信号，我们将能够拼凑出控制大质量恒星演化的物理原理，以及它们是如何结束生命的。

Black Holes and Neutron Stars are some of the strangest objects in the universe, containing moremass than the Sun packed into a sphere only a few kilometres across. They are formed from theremains of high mass stars, which burn their fuel quickly and end their lives in supernovaexplosions which can outshine a whole galaxy. There are different types of supernova for differenttypes of stars: their masses, spins and composition all play a role in determining their eventualfate, although the details are not fully understood yet.What is left over after the supernova is an object so dense that its gravitywarps the space-time around it: a neutron star is thought to contain the densest possiblematter, denser than an atomic nucleus, which is the only material strong enough to support the staragainst its own gravity. Even more extreme are black holes, which form when a star has even more mass,and neutron star matter cannot support its weight. When this happens the star collapses into a blackhole, becoming so dense that not even light can escape the gravitational pull. At this pointan event horizon forms, hiding its contents from the rest of the universe. Since black holes donot emit light, they are impossible for astronomers to find unless they are actively accreting materialfrom a companion star. But there is another way to detect them using a completely new astronomicaltool: gravitational waves.According to Einstein's theory of General Relativity, when black holes and neutron stars are foundtogether in a binary system, the movement of so much matter in such a concentrated space createsvibrations in space-time itself. These travel out across the universe at the speed of light, changingthe dimensions of everything they pass through, but invisible to the eye. Back on Earth, physicistshave long been searching for gravitational waves by making extremely precise distance measurementsusing gravitational wave detectors.So far no signs have been found, but soon the Advanced LIGO and Advanced Virgo detectors will becomeoperational with a sensitivity that ought to allow us to detect the gravitational waves from binary neutronstars within hundreds of millions of light years from Earth, and out to even greater distances for the heavierblack hole binaries. The detectors are so sensitive that the change they can measure is equivalent ofvarying the distance between the Sun and Saturn by a hair's breadth.Encoded in the gravitational waves is information about the sources that emitted them, which will let us learnabout the masses and spins of neutron stars and black holes. By measuring many signals, we will beable to piece together the physics that governs the evolution of massive stars, and how they end theirlives.