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The astronomical unit is too small to be convenient for interstellar distances, where the parsec and light-year are widely used. The parsec (parallax arcsecond) is defined in terms of the astronomical unit, being the distance of an object with a parallax of 1″. The light-year is often used in popular works, but is not an approved non-SI unit ...
In terms of this speed, the old definition of the astronomical unit of length had the accepted value: [3] 1 au = c 0 τ A = (149 597 870 700 ± 3) m, where τ A is the transit time of light across the astronomical unit. The astronomical unit of length was determined by the condition that the measured data in the ephemeris match observations ...
astronomical unit (AU) 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 ...
astronomical unit: au length: 1 au = 149 597 870 700 m: degree ° ... The unit is defined in a table of units in the brochure but not accepted for use with the SI.
The basic unit of length in the imperial and U.S. customary systems is the yard, defined as exactly 0.9144 m by international treaty in 1959. [2] [5] Common imperial units and U.S. customary units of length include: [6] thou or mil (1 ⁄ 1000 of an inch) inch (25.4 mm) foot (12 inches, 0.3048 m) yard (3 feet, 0.9144 m)
149.6 Gm (93.0 million mi; 1.0 au) – average distance between the Earth and the Sun – the original definition of the astronomical unit; 199 Gm (1.3 au) – diameter of Rho Persei, an asymptotic giant branch star, fusing carbon into neon in a shell surrounding an inert core. [180] 228 Gm (1.5 au) – distance between Mars and the Sun; 248 Gm ...
The astronomical unit of length is known as the astronomical unit (A or au), which in the IAU(1976) system is defined as the length for which the gravitational constant, more specifically the Gaussian gravitational constant k expressed in the astronomical units (i.e. k 2 has units A 3 S −1 D −2), takes the value of 0.017 202 098 95. This ...
Name of unit Symbol Definition Relation to SI units ångström: Å ≡ 1 × 10 −10 m: ≡ 0.1 nm astronomical unit: au ≡ 149 597 870 700 m ≈ Distance from Earth to Sun ≡ 149 597 870 700 m [1] attometre: am ≡ 1 × 10 −18 m: ≡ 1 × 10 −18 m: barleycorn (H) = 1 ⁄ 3 in (see note above about rounding) = 8.4 6 × 10 −3 m bohr ...