The phrase "island universe" refers to a complete and separate galaxy similar to our own Milky Way galaxy. It implies that galaxies are like individual islands floating in space, each with its own unique stars, planets, and other celestial objects.
Sentences with «island universe»
Kant was right about the nebulae; Edwin Hubble established the reality of island universes in the 1920s. (sciencenews.org)
The theory that spiral nebulae were separate «universes» unto themselves became known as the «island universe theory.» (apod.nasa.gov)
While I don't want to spoil anything, one notable sequence involves taking imprints of various wooden carvings with a block of cheese, and then using the markings on said cheese to manipulate an ancient idol to change the course of the wind — all just business as usual in the Monkey Island universe. (thatvideogameblog.com)