The Evolving Universe

Smithsonian Institution

Andromeda Galaxy • M31

M31 image

Credit: NASA/JPL-Caltech

Observers: Pauline Barmby, CfA

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Persian astronomer Abd al-Rahman al-Sufi made the earliest recorded observation of the Andromeda Galaxy in 964 CE. Along with our Milky Way, this galaxy belongs to a group of galaxies known as the Local Group. Andromeda contains over one trillion stars - about three times the Milky Way's 200-400 billion stars. But watch out! Astronomers predict that the two galaxies could collide several billion years from now.

  • Distance from Earth: 2.5 million light years
  • Size: 260,000 light years
  • Telescope: Spitzer/IRAC
  • Light: Infrared (blue 3.6, red 8.0 microns)