The Milky Way galaxy is the galaxy which contains our Solar System. The name "milky" is derived from its appearance as a dim glowing band arching across the night sky in which the naked eye cannot distinguish individual stars. From the Earth, the Milky Way appears like a band because of its disk-shaped structure is viewed from within the Galaxy. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. In the past, astronomers thought that all of the stars in the universe were contained in the Milky Way.
Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edward Hubble showed that the Milky Way was just one of the galaxies.
The Milky Way is a barred spiral galaxy some 100,000–120,000 light-years in diameter which contains approximately 100–400 billion stars. It may contain at least as many planets as well. The Solar System is located within the disk, about 27,000 light-years away from the Galactic Center, on the inner edge of a spiral-shaped concentration of gas and dust called the Orion–Cygnus Arm.