It is estimated to contain 100–400 billion stars and at least that number of planets. The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster. Recent simulations suggest that a dark matter area, also containing some visible stars, may extend up to a diameter of almost 2 million light-years. The Milky Way is a barred spiral galaxy with an estimated visible diameter of 100,000–200,000 light-years, but only about 1000 light years thick at the spiral arms (more at the bulge). 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.

Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610.

The term Milky Way is a translation of the Latin via lactea, from the Greek γαλακτικός κύκλος ( galaktikos kýklos), meaning 'milky circle.' From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. For other uses, see Milky Way (disambiguation).ĭark matter halo: 1.9 ± 0.4 Mly (580 ± 120 kpc)

Nasa picture of the day milky way