Seiun

Seiun is the romanization of the Japanese term 星雲, which is commonly translated as nebula. In astronomy, a nebula is an interstellar cloud of dust and gas that fills the space between stars. Nebulae come in various forms, including emission nebulae that glow due to excited gas, reflection nebulae that reflect starlight, dark nebulae that obscure background light, and planetary nebulae formed from the ejected outer layers of dying stars. They are key regions in which stars are born or end their lives, and they appear across different wavelengths from visible to infrared.

In Japanese science fiction culture, the Seiun Award (星雲賞) is a major annual prize recognizing achievements in the field. Established in the 1960s, it honors works across multiple categories such as novels, comics, and other media related to science fiction. The award is presented by organizers associated with SF Magazine and is regarded as one of the most prestigious recognitions in Japanese science fiction.

Beyond astronomy and science fiction, Seiun can be used as a proper noun in various other contexts, including branding or project names. Because it is a transliteration of a common Japanese noun, its use as a name depends on the context and is not tied to a single organization or field. In English-language discussions, clarifying the intended sense—astronomy, literature award, or another usage—helps avoid confusion.