The term “quasar” is short for “quasi-stellar radio source.” The term came into general usage in the 1960s, when astronomers studying cosmic radio sources noticed that many of them looked like stars on photographs. Subsequent studies showed that they were not stars at all, but rather active galactic nuclei (AGN). Nowadays, the word “quasar” is often used to mean any quasi-stellar object (QSO), whether or not it emits radio waves.