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Facts about the Milky Way For Kids

Its name derives from its appearance as a dim “milky” glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars. The term “Milky Way” is a translation of the Classical Latin via lactea, from the Hellenistic Greek γαλαξίας κύκλος (pr.

  • The fact that this faint band of light is made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars.
  • The Milky Way is a barred spiral galaxy 100,000–120,000 light-years in diameter containing 200–400 billion stars.
  • The Solar System is located within the disk, around two thirds of the way out from the Galactic Center, on the inner edge of a spiral-shaped concentration of gas and dust called the Orion–Cygnus Arm.
  • Surrounded by several smaller satellite galaxies, the Milky Way is part of the Local Group of galaxies, which forms a subcomponent of the Virgo Supercluster.
  • The center of the Galaxy lies in the direction of the constellation Sagittarius; it is here that the Milky Way is brightest.
  • The fact that the band divides the night sky into two roughly equal hemispheres indicates that the Solar System lies close to the Galactic plane.
  • As a comparison, the neighboring Andromeda Galaxy contains an estimated one trillion (10) stars.
  • Both gravitational microlensing and planetary transit observations indicate that there may be at least as many planets bound to stars as there are stars in the Milky Way, while microlensing measurements indicate that there are more rogue planets not bound to host stars than there are stars.
  • Surrounding the Galactic disk is a spherical Galactic Halo of stars and globular clusters that extends further outward, but is limited in size by the orbits of two Milky Way satellites, the Large and the Small Magellanic Clouds, whose closest approach to the Galactic center is about 180,000 ly (55 kpc).
  • Most of the mass of the Galaxy appears to be matter of unknown form which interacts with other matter through gravitational but not electromagnetic forces; this is dubbed dark matter.
  • The mass distribution within the Galaxy closely resembles the SBc Hubble classification, which is a spiral galaxy with relatively loosely wound arms.
  • Astronomers first began to suspect that the Milky Way is a barred spiral galaxy, rather than an ordinary spiral galaxy, in the 1990s.
  • The bar may be surrounded by a ring called the “5-kpc ring” that contains a large fraction of the molecular hydrogen present in the Galaxy, as well as most of the Milky Way’s star formation activity.
  • Beyond the gravitational influence of the Galactic bars, astronomers generally organize the interstellar medium and stars in the disk of the Milky Way in four spiral arms.
  • In January 2006, researchers reported that the heretofore unexplained warp in the disk of the Milky Way has now been mapped and found to be a ripple or vibration set up by the Large and Small Magellanic Clouds as they circle the Galaxy, causing vibrations at certain frequencies when they pass through its edges.