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Galactic year 

Panoramic image of the Milky Way, taken from death valley.
Panoramic image of the Milky Way, taken from death valley.

The galactic year, also known as a cosmic year, is the duration of time required for the solar system to orbit once around the center of the Milky Way galaxy.[1] Estimates of the length of one orbit range from 225 to 250 million "terrestrial" years. [2]

The galactic year provides a conveniently "graspable" unit for thinking about cosmic and geological time periods. (By contrast, a "billion-year" scale does not allow for useful discrimination between geologic events, and a "million-year" scale requires some rather large numbers.) [3]

Timeline of History in Galactic Years (GY)

See also

References

  1. ^ Astronomy Knowledge Base
  2. ^ Leong, Stacy (2002). Period of the Sun's Orbit around the Galaxy (Cosmic Year). The Physics Factbook.
  3. ^ Geologic Time Scale

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