S2

S2 is an alphanumeric designation used in various fields to denote the second version or variant of a product, object, or concept. It appears in science, technology, and culture as a shorthand for different, unrelated things.

In astronomy, S2 is the name of a star orbiting the supermassive black hole at the center of the Milky Way, Sagittarius A*. The star has a well-studied, highly elliptical orbit with a period of roughly 16 years, and its observations have provided tests of general relativity in the strong-gravity regime.

In biology, S2 cells are a cell line derived from Drosophila melanogaster. They are non-adherent and widely used in molecular biology for gene expression studies, protein interaction experiments, transfection, and RNA interference.

In software and geospatial computing, S2 refers to the S2 geometry library developed by Google. The library provides spherical geometry tools and a hierarchical spatial index used to encode lat/long coordinates into compact integers, aiding proximity searches and mapping tasks.

In media and entertainment, S2 commonly denotes the second season of a television series or other serialized work, often referenced in episode guides and release schedules.

This usage can extend to other domains, including vehicle and product naming, where S2 marks a successor model, revision, or variant.