The coalescence of double neutron star (NS–NS) and black hole (BH)–NS binaries are prime sources of gravitational waves (GW) for Advanced LIGO/Virgo and future ground-based detectors. Neutron-rich matter released from such events undergoes rapid neutron capture (r-process) nucleosynthesis as it decompresses into space, enriching our universe with rare heavy elements like gold and platinum. Radioactive decay of these unstable nuclei powers a rapidly evolving, approximately isotropic thermal transient known as a “kilonova”, which probes the physical conditions during the merger and its aftermath. Here I review the history and physics of kilonovae, leading to the current paradigm of day-timescale emission at optical wavelengths from lanthanide-free components of the ejecta, followed by week-long emission with a spectral peak in the near-infrared (NIR). These theoretical predictions, as compiled in the original version of this review, were largely confirmed by the transient optical/NIR counterpart discovered to the first NS–NS merger, GW170817, discovered by LIGO/Virgo. Using a simple light curve model to illustrate the essential physical processes and their application to GW170817, I then introduce important variations about the standard picture which may be observable in future mergers. These include \(\sim \)hour-long UV precursor emission, powered by the decay of free neutrons in the outermost ejecta layers or shock-heating of the ejecta by a delayed ultra-relativistic outflow; and enhancement of the luminosity from a long-lived central engine, such as an accreting BH or millisecond magnetar. Joint GW and kilonova observations of GW170817 and future events provide a new avenue to constrain the astrophysical origin of the r-process elements and the equation of state of dense nuclear matter.

双中子星 (NS-NS) 和黑洞 (BH)-NS 双星的合并是高级 LIGO/Virgo 和未来地面探测器的引力波 (GW) 的主要来源。从此类事件中释放出的富中子物质在减压到太空时会经历快速中子捕获（r过程）核合成，从而使我们的宇宙富含金和铂等稀有重元素。这些不稳定核的放射性衰变为快速演变的、近似各向同性的热瞬变提供动力，称为“千新星”，它探测合并期间及其后果的物理条件。在这里，我回顾了千新星的历史和物理学，导致了目前的范例，即喷射物中不含镧系元素的成分在光波长下进行日尺度发射，然后在近红外 (NIR) 处出现光谱峰值的为期一周的发射。这些理论预测，正如本综述的原始版本中所汇编的那样，在很大程度上得到了 LIGO/Virgo 发现的第一次 NS-NS 合并 GW170817 所发现的瞬态光学/近红外对应物的证实。使用简单的光曲线模型来说明基本的物理过程及其在 GW170817 中的应用，然后我介绍了在未来合并中可能观察到的标准图的重要变化。其中包括\(\sim \)长达一小时的紫外线前驱体发射，由最外层喷射物层中的自由中子衰变或延迟的超相对论流出对喷射物的冲击加热提供动力；以及增强长寿命中央引擎（例如吸积 BH 或毫秒磁星）的亮度。 GW 和 kilonova 对 GW170817 和未来事件的联合观测为约束r过程元素的天体物理起源和致密核物质的状态方程提供了一条新途径。