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Why were quasars originally called quasi-stellar radio sources?
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Quasar
Six quasar host galaxies, as observed by the Hubble Space Telescope.
Shown are apparently normal, solitary galaxies (left), colliding galaxies (centre), and merging galaxies (right).
Quasars were originally dubbed "quasi-stellar radio sources" because of their appearance in early radio surveys of the sky conducted in the 1950s. When astronomers identified these radio sources, they observed that the objects appeared as unusually blue stars, rather than the galaxies typically associated with such emissions.1
While some of these objects were later found to be embedded in faint, fuzzy halos, their almost starlike visual characteristics led to the descriptive name "quasi-stellar radio source." By 1964, this term was shortened to "quasar".1