Star formation is a fundamental process for galactic evolution. One issue over the last several decades has been determining whether star formation is induced by external triggers or is self-regulated in a closed system. The role of an external trigger, which can effectively collect mass in a small volume, has attracted particular attention in connection with the formation of massive stellar clusters, which in the extreme may lead to starbursts. Recent observations have revealed massive cluster formation triggered by cloud-cloud collisions in nearby interacting galaxies, including the Magellanic system and the Antennae Galaxies as well as almost all well-known high-mass star-forming regions such as RCW 120, M20, M42, NGC 6334, etc., in the Milky Way. Theoretical efforts are laying the foundation for the mass compression that causes massive cluster/star formation. Here, we review the recent progress on cloud-cloud collisions and triggered star-cluster formation and discuss the future prospects for this area of research.

中文翻译：

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云-云碰撞和触发恒星形成

恒星形成是星系演化的一个基本过程。过去几十年的一个问题是确定恒星形成是由外部触发诱导还是在封闭系统中自我调节。外部触发器的作用可以有效地在小体积内收集质量，在大质量星团的形成方面引起了特别的关注，在极端情况下可能会导致星暴。最近的观测揭示了由附近相互作用星系中的云云碰撞引发的大规模星团形成，包括麦哲伦星系和触角星系以及几乎所有著名的大质量恒星形成区域，如 RCW 120、M20、M42、银河系中的 NGC 6334 等。理论工作正在为导致大量星团/恒星形成的质量压缩奠定基础。在这里，我们回顾了最近在云-云碰撞和触发星团形成方面的进展，并讨论了这一研究领域的未来前景。