Jets, collimated outflows of particles and fields, are observed in a wide variety of astrophysical systems, including Active Galactic Nuclei of various types, micro-quasars, gamma-ray bursts, and young stellar objects. Despite intensive efforts along several decades of observational and theoretical research, there are still many uncertainties and open questions related to how jets are produced and what is their composition. In this review, I offer an outline of some current views on the content and basic properties of astrophysical jets.

中文翻译：

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天体物理喷流的内容

在各种天体物理系统中都可以观察到喷流，即粒子和场的准直流出物，包括各种类型的活动星系核、微类星体、伽马射线爆发和年轻的恒星物体。尽管在数十年的观测和理论研究中付出了大量努力，但仍然存在许多与喷流如何产生及其成分有关的不确定性和悬而未决的问题。在这篇评论中，我概述了目前对天体物理喷流的内容和基本特性的一些看法。