The
Milky Way is the
galaxy that contains our
Solar System. Its name "milky" is derived from its appearance as a dim glowing band arching across the night sky whose individual stars cannot be distinguished by the naked eye. The term "Milky Way" is a translation of the
Latin , from the
Greek (, "milky circle"). From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within.
Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the
Universe. Following the 1920
Great Debate between the astronomers
Harlow Shapley and
Heber Curtis, observations by
Edwin Hubble showed that the Milky Way is just one of many galaxies—now estimated to number as many as 200 billion galaxies in the
observable universe.