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  2. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec. [6] One au is equivalent to 499 light-seconds to within 10 parts per million.

  3. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    The astronomical unit of length is now defined as exactly 149 597 870 700 meters. [4] It is approximately equal to the mean Earth–Sun distance. It was formerly defined as that length for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and ...

  4. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 ...

  5. Parsec - Wikipedia

    en.wikipedia.org/wiki/Parsec

    The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).

  6. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    Direct distance measurements are based upon the astronomical unit (AU), which is defined as the mean distance between the Earth and the Sun. Kepler's laws provide precise ratios of the orbit sizes of objects orbiting the Sun, but provide no measurement of the overall scale of the orbit system.

  7. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    The petametre (SI symbol: Pm) is a unit of length in the metric system equal to 10 15 meters. To help compare different distances this section lists lengths starting at 10 15 m (1 Pm or 1 trillion km or 6685 astronomical units (AU) or 0.11 light-years). 1.0 Pm = 0.105702341 light-years

  8. Canonical units - Wikipedia

    en.wikipedia.org/wiki/Canonical_units

    The astronomical unit (AU) is the canonical distance unit for the orbit around the Sun of the combined Earth-Moon system (based on the formerly best-known value). The corresponding time unit is the (sidereal) year)), and the mass is the total mass of the Sun (M ☉). [a]

  9. Glossary of astronomy - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_astronomy

    A unit of length used primarily for measuring distances within the Solar System or secondarily between the Earth and distant stars. Originally conceived as the semimajor axis of the Earth's orbit around the Sun, the astronomical unit is now more rigidly defined as exactly 149,597,870.7 kilometres (92,956,000 miles; 4.8481 × 10 −6 parsecs; 1. ...