Multi-messenger astrophysics, a long-anticipated extension to traditional multiwavelength astronomy, has emerged over the past decade as a distinct discipline providing unique and valuable insights into the properties and processes of the physical Universe. These insights arise from the inherently complementary information carried by photons, gravitational waves, neutrinos and cosmic rays about individual cosmic sources and source populations. This complementarity is the reason why multi-messenger astrophysics is much more than just the sum of the parts. In this Review article, we survey the current status of multi-messenger astrophysics, highlighting some exciting results, and discussing the major follow-up questions they have raised. Key recent achievements include the measurement of the spectrum of ultrahigh-energy cosmic rays out to the highest observable energies; the discovery of the diffuse high-energy neutrino background; the first direct detections of gravitational waves and the use of gravitational waves to characterize merging black holes and neutron stars in strong-field gravity; and the identification of the first joint electromagnetic plus gravitational wave and electromagnetic plus high-energy neutrino multi-messenger sources. We discuss the rationales for the next generation of multi-messenger observatories, and outline a vision of the most likely future directions for this exciting and rapidly growing field.

在过去的十年中，多信使天体物理学作为对传统多波长天文学的长期期待而出现，它作为一门独特的学科提供了对物理宇宙的特性和过程的独特且有价值的见解。这些见解来自光子，引力波，中微子和宇宙射线关于单个宇宙源和源群所固有的互补信息。这种互补性是多信使天体物理学不只是各个部分之和的原因。在这篇评论文章中，我们调查了多信使天体物理学的现状，重点介绍了一些令人兴奋的结果，并讨论了它们提出的主要后续问题。最近的主要成就包括测量超高能宇宙射线光谱到最高可观察到的能量；发现弥散的高能中微子背景；首次直接检测引力波，并利用引力波表征强场引力中合并的黑洞和中子星；并确定了第一个联合电磁加引力波和电磁加高能中微子多信源。我们讨论了下一代多信使天文台的基本原理，并概述了这一激动人心且迅速发展的领域最有可能的未来发展方向的愿景。首次直接检测引力波，并利用引力波表征强场引力中合并的黑洞和中子星；并确定了第一个联合电磁加引力波和电磁加高能中微子多信源。我们讨论了下一代多信使天文台的基本原理，并概述了这一激动人心且迅速发展的领域最有可能的未来发展方向的愿景。首次直接检测引力波，并利用引力波表征强场引力中合并的黑洞和中子星；并确定了第一个联合电磁加引力波和电磁加高能中微子多信源。我们讨论了下一代多信使天文台的基本原理，并概述了这一激动人心且迅速发展的领域最有可能的未来发展方向的愿景。