noun
spiral nebula
Obsolete astronomical term for what is now called a spiral galaxy. Used historically before the nature of galaxies was fully understood.
19世紀の天文学者は、アンドロメダを渦巻星雲と呼んでいた。
In the 19th century, astronomers called Andromeda a spiral nebula.
Modern term for a spiral galaxy, replacing the obsolete 渦巻星雲.
Compound of 渦巻 (spiral) and 星雲 (nebula). The term reflects early astronomical classification before the distinction between nebulae and galaxies was established.