電波星系和相關的電波喧噪類星體和耀变体，都是在無線電波長（頻率在10 MHz到100 GHz，功率高達10^38 W）上非常明亮的活躍星系。電波的輻射來自於同步加速過程，被觀測到的電波是來自於一對氣體噴流的結構和外在的媒介，經由相對論性發光修正的作用後所發射的。電波喧噪的活躍星系令人感興趣的不僅是星系本身，還因為它們可以在遙遠的距離外被觀測到，可以做為觀測宇宙論上可貴的工具。最近，有很多工作有效的從這些星系際介質，特別是星系團，得到了很好的結果。

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Stay warm, walk steady, close your eyes. 夏恋

Ontology (from the Greek ὄν, genitive ὄντος: “of being” (neuter participle of εἶναι: “to be”) and -λογία, -logia: science, study, theory) is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology deals with questions concerning whether entities exist or can be said to exist, and how such entities can be grouped, related within a hierarchy, and subdivided according to similarities and differences.

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